Music in Gallery

Hello.. i am using gallery 1 ovviously, and i've been searching all around the fourms but i still cant figure it out. I read some where that i need to put an embed code for background music, if thats the case where does it go? Also i read that i need to change the classes/albums_user.php or some file similar to that...
but i cant figure it out. I need like a step on step way on how to insert music for dummies. i'm talking about an mp3. thanks for the help!