Note: A Murfie HiFi membership is needed for lossless streaming.
1. Go to the Membership section page of your Murfie account and change the streaming setting from standard to HiFi. (Note: If you already have Murfie on Sonos, be sure to clear your playlists, queue, alarms, and Sonos Favorites before changing this setting.)
2. Open your Sonos Controller App (iPad, computer, phone, etc).
3. In the main Sonos menu, go to "Add Music Services" Click on “Murfie” (look for the pink icon with a white “m”)
4. Sign in with your Murfie credentials
Read more on How to add a music service to Sonos (source: Sonos Support).