There are two ways
1. Link / button to the MP3
This is the safest method:
Upload your MP3 file to a publicly accessible URL (your website, CDN, cloud storage with a direct link).
In Stripo: add a Button or a “Text with link” block (or image + link) that says something like “Listen to audio” or “Download MP3”.
Link the button/text/image to the MP3 URL (or to a page that plays it).
Optionally add an image (album cover, audio icon) for visual context next to it.
Embed audio using custom HTML block
If you want to attempt an embedded audio player:
In Stripo, add a Custom HTML block (Stripo supports HTML blocks as one of its basic blocks).
In that HTML block, insert markup like:
<audio controls>
<source src="https://yourdomain.com/path/to/file.mp3" type="audio/mpeg">
Your browser does not support the audio element.
</audio>
Set up the source URL (src=…) to the MP3 you uploaded.
Then test the email in multiple clients.