There are two ways you can play B2 music on a Sonos system.
One way uses the Sonos app for control. It uses the B2 hard disk as a NAS drive and reads from it. If you want to use this way, you will need a device on which to run the Sonos app - smart phone, tablet, or computer. Of course, you'll need the same sort of device to run the B2's WebUI too.
The other way is for the B2 WebUI to control the system by sending music to the Sonos system.
There are pros and cons to either method. I don't do Sonos, so I will leave it to others to go into more depth, if you want it.