They would just connect as normal, and utilize the system as you have set it up. The only reason they would need your account information would be if they were be adding new streamers to your system. 

To be ultra clear, other users just need access to your WiFi, and they have access to your Sonos. There is only one Sonos account (yours) which can change the setup. 

Yes it is solved thanks.  I had to turn on “access local network” for the Sonos app and the system appeared.  Thank you for the quick reply!