Thread:Project:Support desk/Editing "Login Required" Page.

I currently have my company Wiki setup so that only registered users can view the pages. If they are not registered (or logged in) the standard "Login Required" page shows up. I would like to edit that page so that it gives an explanation of why the wiki is locked and who they can contact to get approval to join. I cannot for the life of me figure out how to do this!! Any tips would be helpful.