First, your gonna have to go onto yt and search up a song or anything. Next copy the link of that video. Now just go onto google and search up yt mp3 or go to this link: https://ytmp3.cc/en13/
Alright after converting it, download it and go back to myspace and login. After make sure your on your home page and you should see a comment saying "Edit Mp3". Click on it and click on the file you wanna use for the song. There you go!