making ringtones from my music app.

[Heather SunnyChaos]

i just got a skyrocket. I want to use the factory music app for some of my ringtones.
is there a way to do that?
(i got this from a mobile store.. the person who had the phone put music on it.. so i like some of the songs.. want them for ringtones.)
any help would be appreciated. thanks.