To play audio that you uploaded to your site using a widget, edit the settings so that the URL looks like http://mysite.yolasite.com/resources/song.mp3, where mysite is the name of your published site and song.mp3 is the name of the music file you've uploaded and would like to hear.
Remember to include any folder names in the file path if your file is stored in a folder in the File Manager. For example, if you have a Music folder, then insert resources/Music/song.mp3.
For more information, please take a look at this link.