Motorola RAZR V3

i just received my razr v3 in the mail today, and i must say its pretty sweet.

i got it with tmobile usa, so i didnt get any software included. in order to transfer mp3s from my pc to my phone, to use as ringtones, what software do i need? im going to go buy a usb to mini-usb cable today, but after i hook my phone up to my pc, what else do i do? if someone could be so kind as to give me step by step instructions or give me a link with a walkthrough, id greatly appreciate it. thanks!