i am gathering that your an admin on the board *S*
this is an easy way to do it
log into admin, then go to boards, find the board you wish to use, click on modify, look for "Allowed Groups" then you will see a list, guest, member, the name of any member groups, make sure there is NO ticks in any box, remember to click the modify button down the bottom, then the only person who can access that board to write on it or see it is you. If your setting a board up for it, its the same process.
if your wanting to do something that your members can read but cant reply, there is a section in the modify board to make it "read only"
hope that helps *S*
oh and im just a fellow member here *S*