Pantech Reveal C790

Does anyone with a pantech reveal know how to set a downloaded tone as a text alert? i downloaded a sound i'd like to use as a text alert but i can't figure out how to set it- i'm stuck with choosing from one of the 8 sounds that comes with the phone- the sound i downloaded cannot be moved into the "alert tone" section of the audio file so i dpn't know what to do---someone Help!