Watch: Student One creates the group site
The first part of the group video: one student registers, starts the site, and turns on Allow Link.
The first part of Registering as a Group Website is Student One only.
That student registers, signs in, clicks Start Now, writes down the site key, and clicks Allow Link. Everyone else has 24 hours to join. Student One can click Allow Link again to open another 24 hours.
The written steps are in Register a group website.