There are two ways that you can do this:
A) You can create the forum, visit the Settings -> Permissions page, and then Prevent the "mod/forum:viewdiscussion" capability for the "Guest" role.
This will mean that the forum is listed on the site homepage, but trying to view the forum will redirect the user to the login page. Authenticated users will be able to interact with the forum as normal.
B) Add an Access Restriction based on a profile field - if you set a restriction like: "Email address is not empty" and then press the eye icon, then it will be hidden for guest users, and visible to logged-in users.
Hope this helps,
Andrew
Forum
Creating a single main Forum for all students
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