Samsung SGH-T619

i was able to have a friend transfer music to my phone via bluetooth, but now i can't figure out how to make my mp3s into ringtones. when i try to, the options "ringtone" and "caller ringtone" are greyed out, but "alarm tone" is the only highlighted option. does anyone know how to make the mp3 files in this phone into a ringtone or caller ringtone? or is it just not possible? =(