If your local fish store is a good one just follow their advise. Don't be surprised if they suggest you spring for a new filter system. Their are cheap enough for a 10 gallon and you don't want to risk getting set up and losing the tank to ick or such. (Ick is a parasite that can survive under extreme conditions).
Before you take the tank and such out of the shower wash everything in the hottest water you can stand, but do not use any chemicals. Then let it dry in full sunshine for a day.
Start your tank with only a few fish. No more than 3 or 4. Neons are a good bet, they are hardy and colorful. Head and tail light are another. You'll need a heater (about $30 for a good one) if you get tropical fish. Your standard comet will not need a heater, but then you are limited to comets.