Just a wee bit from my experience with creating new forums in here (have fun Eru and Din!! )
After you create them, you have to individually review access for each user through user management / user permissions.
A bit of work but if you use the list of names in this forum, it should be done fairly quickly.
... and who knows, maybe there's an easier way... only me don't know about it
Good luck - it's fun messing with settings