You can stream your purchased music through Apple Music on the Sonos app or AirPlay the music directly to Sonos from your phone from the Apple Music app. You can also add your music library stored on a computer or NAS to Sonos by following these instructions:

https://support.sonos.com/en-us/article/add-your-music-library-to-sonos

Every time I try to add it, the app says “we’ve run into a problem, try again.”

Hi @ctfeher, 

If you’re running into issues adding your Music Library to Sonos. I’d recommend submitting a diagnostics then reaching out to our support team for further assistance. They have the tools available to help troubleshoot and resolve this issue with you. 

I hope this helps!