The best thing to do is make your own Myspace Music profile, as if you were a band or something.
Go to Myspace Music, sign up as if you were a band. Title your page whatever you want but dont waste time on decorating it or anything. Don't even add any friends. Let it just be a blank page. Download whatever song you want on to your computer. Add that mp3 to your music player. The song-adding feature guides you through this process. It's very easy. Then log out of that account, sign into your personal account, and add your own song to your page.
I have my own music player and it's great. It allows you to essentially put up whatever song you want. Just don't name the profile after the band you want to put up, liek Stone Tmeple Pilots, because there's a chance it'll be deleted. For example, I titled mine "vincespace music".