OK....You have a bio filter which is an excellent filter. But the thing you need to remember is that its going to take a few day up to a few weeks for it to start working properly...you have to get the GOOD bacteria growing in it
So what you need to do, is get all the gravel and stuff set up...Let me back up a bit
I have had tanks all my life...I just took down a 55 gal that I had up for YEARS to make room for...you guessed it...BIRDS...Anyway, I prefer to use two types of filters...I had the bio filter on the back and then I also had an underground filter with a power head that drew the water down through the gravel so it acts as a stratusphere and helps take care of all the waste. It also helps keep the water airiated (sp) so the oxygen level stays up.
What I would do is take regular old table salt and and it to water and scrub the tank down... Or you can even just use bleach water at like 25% scrub it out and rinse it real well...
Chlorine in tap water disipates after 24 hours...so if you wanted you could just fill the tank up with tap water and let it sit for 24 hours before you put any fish in it But there's several products on the market that will take the chlorine out and condition the water so the fish don't lose their slime coat. No matter how you do it the water should be allowed to cycle for 24 hours before putting fish in it.
Unless your going to only be having gold fish in the tank you will also need a heater and the water should be kept between 72 to 80 degree's no warmer... I tried to keep mine at about 74-76
The type of fish you want to have will determine what the PH level should be. But for a community tank with several kinds of fish in it I kept mine around 6.8 - 7.0 or fairly neutral
Some people start out by adding chemicals to raise or lower the PH. Unless you know your water is extremely acidic or alkeline.. I wouldn't add chemicals to start with to balance it cuz its gonna change soon as you start putting fish in it.
So now, after you've got your tank set where you're going to have it and all the gravel and decorative plants and features are in place fill it with luke warm to cool water...warm water has less oxygen content. Turn your filters on and the heater and allow it to start cycling, watch the water temp so it doesn't go above like 78 Remember the warmer the water the less oxygen.. After its cycled for 24 hours you can start adding fish...BUT just a few...And my fish of choice for beginners and a new tank are Mollies...Black mollies Just plain old not fancy black Mollies...they are really a hardy fish and can withstand a large variance in PH levels with out getting too stressed. for a 30 gal. tank I'd get 4 mollies to start. What you're trying to accomplish now is getting the good bacteria started in the tank filters....You don't want to over populate the tank because them the ammonia levels get way too high and fish start going belly up. There's also a few products on the market that you can get that will start the bacteria growing faster, so if you're an impatient person then you can get that and put in. Ask the dude that sold you the filter.
SO now...you've got 4 fish in the tank...leave them in there for 24 hours and only feed them a small pinch of food...just enough that its all cleaned up in 5 minutes...otherwise it goes to the bottom, rots and causes ammonia to be given off...Ammonia is BAD! It is NOT your friend!

Feed the fish twice to 3 times a day but only what they'll clean up in 5 minutes. NOW, things to start watching for... Stress...are the fish hanging at the top of the tank only? This can be caused by several things...They're too cold...Warm water rises...or if they keep tapping the top of the water like they are trying to feed it could mean that there's not enough water movement to cause the oxygen exchange and they're basically gasping for breath... In which case you need to increase the water flow...this very seldom is the case.
If the fish are hanging to the bottom of the tank it could mean they are too warm... colder water at the bottom of the tank. You want them to be swimming at all levels throughout the tank and being fairly active but not zipping back and forth across the tank but not just staying in one place.
After a week, you'll want to do a partial water change...about a 1/3 of the water needs to be siphoned out and replaced with fresh water, tap water that's been dechlorinated by being left set for 24 hours or treated with chemical... Pour it in slowly to the tank and allow it to cycle...you don't need to take the fish out. Now you need to continue monitoring the fish to watch for stress...check the PH... try keeping it as neutral as you can. Also watch for signs of illness. The most common is ICK...little white spots on their bodies, usually starting on the tail fin and dorsal fin. but can appear all over. This is caused by rapid temp change mainly. So make sure that your tank is staying pretty level temp wise. If you need to adjust the heater do so in very small increments...and if the heater you have has a temp gauge as to where to set the dial, don't trust it to be accurate.
Then after the first water change and the fish are still doing well...active and eating not floating belly up at the top or sunk to the bottom...you can start adding a FEW fish... If you plan on having a community tank with several species of fish you want to make sure that they are all pretty docile fish, not aggressive... And for beginners the hardier fish are ones like platys and guppies and mollies and zebra dannioes (sp) and that type of thing...You can also get fish like neon tetras at this time...but ONLY A FEW at a time...I would add no more that 4 fish at this time... When you add fish, float the bag they come in on top the water for 1/2 hour to an hour till the water temp is about the same...then open the bag and add about half as much more water as is in the bag into the existing water...this gets them used to the PH....after 15 minutes or so do that again...after about another 15 minutes you can allow the fish in the bag to swim out continue to do this process don't over feed and montior the PH...in another week do a 1/3 water change again. If things are staying pretty constant PH wise you can add a few more fish. Don't over crowd... Fish do best when there are at least 3 of each species to school together. Depending on what type of fish you get, I prefer 3 to 5 of each type so you can watch them move in schools. Guppies, mollies and platys and swordtails are all Live bearers meaning they will have live babies and not lay eggs. But if things aren't done to protect the fry, they will be eaten by the adults and other fish. So they need hiding spots with different types of plants and stuff they can get into to hide. Remember, Guppies and Mollies are the "rabbits" of the fish world...
After about a month or maybe even two you'll want to start adding bottom feeders, like cat fish and coulie loaches to help clean up all the extra food that has dropped to the bottom of the tank. You will also want to get an algae eater of some type...I prefer the plecostomus...but there are chinese algae eaters too...they will help keep the algae population down. One or two SMALL plecostomus' per tank is more than enough...especially at this point. Cuz there isn't much for them to eat in there. You can also feed them green beans, uncooked but canned green beans and just drop 1 or 2 in the tank and they'll be able to eat those and not starve. Then you can start changing water once a month and make sure that you change the filters in the bio/back filter as well.
Again its important not to over crowd your tank...so you have a thirty gallon tank so they say 1 inch of fish per inch of surface So measure the tank width...and keep in mind thats the TOTAL inches of fish you should have. I usually think of each fish as 1 inch long unless you know that they are bigger than that... so if your tank is for instance 15 inches wide... no more than 15 fish...and that's SMALL fish...
I would also suggest you start out with the lesser expensive fish...guppies, mollies, platys swords etc. so that you aren't out a bunch of money if some of them go belly up.
Look for some books on Community Fish Tanks and it will help give you ideas of what fish are compatible etc. Tetras and most live bearers goe well Barbs are pretty aggressive...but depending on which kind you get, Ask if a sales person if you aren't sure!
Sorry this is long, but I hope it gets you started...
Remember you can always PM me