All you have to do is unzip members.zip in the forums folder and only registered members of the forum that you have designated as Moderators or Administrators can view the page.  Then you can just put whatever you don't want anyone else to see on the page.  If you're language is English, then you won't have to change anything, but you need to add an error message to match the 'Not Member' reference on line 73 of members.php (You would add the error message in the language file... just like I did on line 17 of en_common.php).

Here is the link to the mod:
members.zip

Hope this helps.....