Kingdom hearts 1... Please help!!?

O.K so im at the part were you have to defeat Ursula at Atlantica or somthin like tht! Its were ariel is is! And i need some tips or walk throughs on how to defeat her or what the heck you do! You can tell me now, on instant messager, or give me a web site that has that perticular cheat on it! Thanx much!