If you want to make a forum only viewable by a certain group then this tutorial will show you how.

Steps :
Log into your forum admin panel then click on Permission under Forum Admin. Select the forum you wish to make private then click Look up Forum. You can decide to make your forum private or private [hidden] which basically means you can make only people that are a member of that group see the forum name when it's hidden. Choose either of the two.

Create your group that you want to allow access to the private forum [Tutorial on how to create groups in the tutorial section].

Click permisson under Group Admin then select the group that you want to allow access to the private forum and click Look up Group. You will notice a drop menu beside your private forum name asking to allow or disallow access. Select allow access. Click Submit and you are done. Now only members of that group will be able to view the forum.

That's all! More help visit our forums.