Click the drop down arrow on "Audio."\
Click "Audio from File..."
4
Select a song you already have saved to your computer.\
Click "Insert."
Change Song Playback Settings
5
Click on the Speaker Icon.
6
Click "Playback"
7
Click "Play in Background" for your song to play on a loop in the background of your entire presentation.
You can also adjust settings such as fade in/out, when to start/stop, looping, captions, and more.