To play music on your Sonos speakers with the Home App, you have to add music in the Sonos app to «My Sonos» first. This works as follows :

1. Open the Sonos app.
2. Browse your music in the «Browse» or «Search» tab.
3. Tap the three dots of the desired album, song, playlist or radio station.
4. Choose «Add to My Sonos». 

The music now appears in the Swisscom Home App in «My Sonos».