After extracting the file, There will be 2 things inside of it

The first is the songs folder where you can add/remove mp3 files. You can also create subfolders inside songs and the mp3 files inside them will also be played.

The second will be a file MP3Player which is the actual app(.app).
For some reason, You need to open it twice and it takes a solid half minute to load

If you want to move the app for whatever reason, Make sure to move the songs folder into the same directory as the app

You need to bypass macOS Gatekeeper because it quarantines the app and I don't have a dev account

Just run the following command, replacing MP3Player/MP3Player.app with path to the app
xattr -rd com.apple.quarantine MP3Player/MP3Player.appp