WhatsApp Help Center - How to use Messenger Rooms
How to use Messenger Rooms - Create and share a room link Open WhatsApp Web or Desktop, then click Menu or above your chats list > Create a room. Alternatively: Open an individual or group chat, then click Attach or > Room. Click CONTINUE IN MESSENGER. This will take you out of WhatsApp and through to the Messenger website in your browser. Since rooms take place outside of WhatsApp and Messenger is a separate website, the Facebook terms and practices will apply.
Note that if you're not logged in to Messenger, you'll need to log in with your Facebook account. Join a room as the invitee. Open WhatsApp Web or Desktop > the ...