The PW system uses the Play-Fi app to support full home control of your music system, it also uses Spotify Connect to stream content from your phone/tablet/PC to your PW devices.
While on the device you want to stream from. Open the Play-Fi app and select Music from the top of the list.
You will now be able to see local content, and sort it based on Artist, Album, Band, Genre, etc...
Internet Radio is a default app available through PlayFi. If you have an existing streaming membership to a service, select it from the list of available sources and follow the set-up instructions.