That is correct! that message is telling you that you are running phpBB in accordance with with their recommendations! (if you typed the message correctly!)
This is also as it should be and is the default setting for PHP5 on DreamHost. If register_globals are ON on DreamHost, you must be running PHP4 (and you really shouldn't be if you can possibly avoid it).
Please don't do that! You can, but you shouldn't.
That said, to learn how to do it - search the forums or the wiki - the answers are there (I think it's irresponsible to help someone do that to run phpBB)