Instructions
Log in to your level with Roblox Studio.
Click on the object you would like to add music to.
Click "Insert" from the top toolbar, mouse over "Services" and then click "Sound."
Click the "Browse" button in the tab. A standard Windows explorer window will appear.
Locate the sound file you would like to upload and click "OK." Copyrighted music will not play in the game, even if it will initially upload. It may take a few minutes for the file to upload, depending the file's size.
Click "OK" to close the window and save the sound to the object.