how to allow manually what members have access to a private forum?
 

even if forum is set for certain users the others still can see the forum's Title in the forums index, I dont like it. they cant access it but they can view its name.

you do this through the use of user groups or access masks in your admincp.

something related, how can the forum be seen only my the permissive group. is that possible?

See "Forum Permissions" and "User Group" (edit permissions) in your AdminCP.

It's very possible; I run a board with 3 sections, public and two levels of private. I have 3 main user groups, one who can see both levels of private and the public subforums, and one who can see only one level of private subforums as well as the public ones, and a group who can only see the public subfourms.

It all works out very well; I've grown to love vBulletin for the amount of micromanagement control it gives over permissions.

You can also set permissions for users individually through Masks.

thank you tim

so how can I mask the forum's Title in the forums index page?
it has to be invisible for non approved members

someone could help me?

As said, go into Forum Permissions. Scroll down to the forum or category you want to hide.
Click the "Edit" link next to your desired Usergroup.
At the top of that page you have Forum Viewing Permissions. Set the first option,Can View Forum, to no. And if you like, do the same with Can View Thread Content.

Hope this helps!

thanks I found what Edit Mask meant :) this was the last step