Points? I'm not sure I know about any points? To PM someone you just click on their username and select "send private message"...or I might be overtired and missing something important...
I think it should say 'posts' not 'points' - basically 5 responses or 5 threads or any mix of either to be able to unlock that feature.
I know a lot of forums won't let you into specific areas or features in your settings/forum sections until you've posted a certain number of times.