Are you talking about your music that you made and you want to promote? If so, you should just create an account on Myspace Music. Once you create your "artist profile", you can upload your music, and then anyone can visit your profile and hear it.
If you're talking about a song you have on your computer that you want to add to your profile, I don't think you can add it. You have to search for songs on Artist's profiles, then click on "ADD" next to the name of the song you want to play.
to add a song to your profile search for the song useing myspace click add and then go to edit profle got to the part that edits your music and click on atomatic start.music donwload