u can't use mp3 as a ringtone in iPhone, u have to convert it to m4r, i normally go to
Start > Music > iTunes > iTunes Media > Automatically Add (first folder)
i drop the new ringtone in Automatically Add folder ....and then open iTunes and check if the new ringtone is under ringtones or not! .....if it is there then connect ur iPhone click on tones and check if the new tone is there and select it and then click sync
there is a free
text tones app which helps u create the right size/format of the text tones
good luck
