This add-on runs librespot on your Hass.io Raspberry Pi.
You can then play music to your speaker connected to your rpi.
When running, you'll be able to connect to it directly from the Spotify App.
Head over to https://github.com/victorcerutti/hassio-addons/spotify-connect for more informations.
Follow repository installation instructions with the url https://github.com/victorcerutti/hassio-addons.