Connect your site to the C5 community. Click 'Extend concrete5' from the 'Dashboard'. Click 'Get More Add-ons' and 'Search' for 'Mp3 Player'.
Purchase, 'Download and Install' and return to website.
Click the '+' icon top left of page as normal and scroll to the 'Multimedia' blocks section you should see the 'Mp3 Player' block.
Drag the block onto your page, choose a 'Poster Image' and an mp3 audio file from your 'File Manager', give it width and height in pixels (same sizes as the uploaded video in the 'File Manager').
Add more if you wish, then 'Publish' your page. Done!