Read the article titled "avoiding and treating new tank syndrome" or something like that at the top of this forum. You need to cycle your water to make sure all of your levels are acceptable before you fully stock your tank. Otherwise you will kill all of your fish. Trust me on this one.
Basically yout have to declorinate your water with stress coat and then you can add some fairly indestructible fish to start the ecosystem: fish pee & poo->amonia(bacteria)->nitrite(other bacteria)->nitrate. If you have $10 you can buy pregrown bacteria. That can drastically reduce the cycling time.