1) Find the forum that you think is most relevent to your post.
2) Click on the New Topic link to start a new discussion in that forum.
3) If you are logged in your message will appear when you click on submit. If you post anonymously it may take several hours for someone to approve it - this avoids spam.
4) If you are logged in you can click on 'Notify me of new posts in the current thread' link at the bottom of the page.
5) To reply to an existing discussion just click on the reply button and add your text.