If you’re using an Apple device (iPhone iPad etc) in most cases it’s a much better to download these MP3 files using a computer first. You’ll then need to add these files via iTunes program, either into your iTunes library or into another chosen App’s folder on your iPhone/iPad.

For adding to iTunes library:

PC Windows   |   MAC   |   Other iOS App

If you’re using an Android device, you may want to first download the MP3’s to a computer to keep a copy, then transfer them onto your mobile device connected to the computer.

Otherwise, MP3’s downloaded directly on an Android device, can usually be played by third-party apps like ‘VLC for Android’ (available free from Google Play), it’s just a matter of knowing where the files have been downloaded to. Downloaded MP3’s will most likely be stored in ‘Downloads’ or ‘Media’ / ‘AUDIO’ folder by default. These can be accessed via ‘Files’/’My Files’ app, but it’s recommended to just open up your chosen media player App (such as ‘VLC for Android’), and open the MP3 files from within that app. This will usually give a better result showing cover art / and track order.

Detailed user guide for ‘VLC for Android’