How Can I?

[Freesteyelz]

In AdminCP (2 easy ways):

vBulletin Options --> Forum Listings Display Options --> Show Private Forums (Option: Select "No")

You can either override the settings for each forum or use the default vB options. To do so go to the forum you want hidden and edit it. In the first section you'll also see "Show Private Forum". For your Moderator forum either select "Use Default" (if in the vB options it's set to "No") or from the drop down menu select "No".