How do I approve someone to a group?

Can you explain how someone gets approved to a group? I want the group manager to be able to do this, but I can't see how it is done.

It is easier to just demonstrate how it is done than to explain it. Please register an acconut on this support forum and go to this page:

User Groups

On the group listing page, you can see a join button by the public group "Test group". Once you click on it you can decide whether or not to send a PM to the group manager to notify application.

As a group manager or an admin of the forum, you will be able to approve/disapprove the membership application by visiting the member listing page of that particular group.