Permissions

Hi,

trying in vain here to set up a couple of users so they are the only members of the site having access to one particular sub forum. For the life of me I just cannot get my head wrapped around how this permission/group thing works in UIEForum. I've set up a new role, I've asssigned this role to the particular users, I've given this role permission in the standard Drupal permissions area but still other users are allowed access to this sub forum.

Could someone please explain this system for my poor simple brain to understand ?

Thanks
Keith