Look in the upper left corner of the page, above the crimespace title banner. You should see your profile pic (tiny) and next to that an envelope graphic. The envelope is the icon for PM's. Also, when you go to a member's page, look just under their profile pic. There's a link that says something like "send this member a message." If you click on that, you'll go to the mail program and be able to send that person a PM.