How can I transfer shortened mp3's to my Motorola Krzr and make them my ringtones?

I already have Motorola Phone Tools v5.0 and I have transferred the shortened mp3's to my phone but the mp3 only shows up in the audio part of the phone. Is there a way to change the audio file to a ringtone and how would I go about doing that?|||ventones.com is completely free. It's not one of those $9.99/month type of scams. You just upload the song, edit which parts you want in the ringtone, then it sends to your phone as an MMS message (pix message or multimedia message). Then you download it to your phone and set as your ringtone!