PM is Private Message. Click on the "My Home" link at the top of the page.

And a tip: Don't argue with the board admin if you want to keep using the board. The BBS is a private entity and he's got the right (and the power) to delete anything on the board for any reason, or ban any user for any reason.

Remember that he's not in a position to decide upon the legality of a given matter, his primary goal is to avoid even the appearance of things illegal. The site's host could easily shut the board down if they thought there was something to be suspicious of. We simply don't want there to be any reason to shut the board down, so the board members need to behave.