My Profile > My MP3's > Upload new.

Make sure that the music you are uploading is either a song written and played by you, or a cover, played by you. Copyrighted versions arent allowed eg. dont post teen spirit by nirvana

Also, make sure the audio file is in mp3 format. Most itunes import in aac as default. to convert go to Preferences > advanced > importing > import using, and select mp3 at 128kbps. Then right clicke the audio file in question and select convert to mp3. if you are not using itunes and cant figure out how to convert, use http://www.zamzar.com. It will convert it for you and email you a download link.