Click Site Members then Pending.
You'll see a list of pending requests to join the site.Tip: You can also click Tasks then My Tasks to get to the approval task, or access it direct from the notification email that was sent.Note: You'll also see any Pending Invites. From Alfresco One version 5.1 or later, users are added to sites and invites are only sent if your Alfresco Administrator has specifically configured this option.
Click Approve, or click View to view the
approval task where you can approve, reject, and comment on the request to join.
The task is cleared from your task list and the user is added to the site.