Another excellent Apple Support video. This one walks through the process of syncing your Apple TV watching experience with other folks on a FaceTime call.
Interesting that the Mac is not mentioned, even though SharePlay via FaceTime was introduced in macOS Monterey 12.1, as described here.
No matter, good to see the SharePlay process in action. Well done.
UPDATE: Note that everyone on the SharePlay needs to be in the same Apple Store Region (no simultaneous watching with folks from UK and US, say). [H/T Samir Estefan]