-You must gain at least 50 QL user points to be approved.
-QL Points are a measure of your activity in QL. TO gain points you must participate in any topics or answer questions.
-If you have 50 or more points, click on "GROUPS", look for the group name and click "SUBSCRIBE.
-To check if your subscription is approved, go to "my groups" or check "My account". Sometimes approval takes time since we may be busy

hope it helps