Scroll down below the central adverts to post new messages, and scroll on past the new message pane to see other people's posts.
But please:-
keep it legal, decent, and truthful
respect
other
people's right to disagree with you
And please make sure you put something in the Name, Subject and Message boxes. It's fine to use an alias, but if you leave any of these boxes blank, you will see an error message and no-one else will see your message.