You cannot connect a Bluetooth adapter to the Play:3. You need to set up the Play:3 in the Sonos app. After you complete the setup process and the Play:3 is connected to your WiFi network, you will be able to stream music to the Play:3 directly from the Sonos app.

Thank you. What threw me is that when I go into the Sonos app it isn’t finding the speaker. When I open the app the system option in the rightmost tab is greyed out. Any idea why that would be / what im doing wrong? Thanks

If you have moved to a new house with a different WiFi network, you need to follow the instructions in this article:

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network?language=en_US

Thank you. I have factory reset it, then gone into the app and can hear the noise chime on the speaker during set up. But once set up is complete and I try to go onto the app to play music, the music tabs are greyed out and it says “Play:3 (unused) not registered” in settings and when I go into that it then says a factory reset is needed to add the speaker to a new system. I’ve been through that twice and get to the same point in set up each time. Any idea?

Try wiring the Play:3 to the router with an ethernet cable and redo the setup process.