ipone ringtones,umm how do u do it?

I have this app that lets me create ringtones,so i create em but i have no idea how to get it from the app where i created them to my ringtone section in my phone,it dsnt let me save it or it goes somewhere?? i have no clue.anyone kno w anything about ringtones? i need to hear my music play,not a duck quacking..i have a 3gs.thnx!