How do I install my dryer?

Our new gas dryer got dropped off today, but the guys wouldn't install it because, due to a new legal code or whatnot, the dryer has to sit on something 18" or higher in order to prevent gas leaks. I don't know what this is all about. We've always had our dryer just sitting on the floor. We don't need something under it. Anyway, I plan on doing it myself, but it says you need some sort of sealant for the pipe adapters, as well as tester fluid. What are these things and where can I find them? Thanks so much.