Since the solution of first post doesn't work anymore at the moment, for now another easy solution is to upload your mp3 file here :
http://www.mp3songurls.com/It'll give you multiple links, including an embed link and other stuff but that's not what we want here, we'll want to take the .mp3 link they've given us

In my case it is "
http://free.mp3songurls.com/1412665.mp3"
Then the rest is just as Raven's tutorial goes, click on "Profile ==> Forum Profile" then paste it in "Profile Song"
I think there's a limit in how long the file stays uploaded if you don't have an account so just create one if you don't want to bother having to re-upload your music everytime.