I've received a few emails from people wishing the forums explained, so I thought I'd put together a little bit of an introduction.
Once you've registered for the forums, you'll be able to view and reply to other posts that have already been made or start a new topic.
Start a new topic
To start a new topic, head into the forum that best suits what you want to say (something Hermione related, go to the "Memories of the Hermione"; something you'd like to see on the website, go to "Site Feedback" etc.).
Once there, in the top right corner (above Last Post), you'll see two buttons: "New Topic" and "Subscribe". To start a new topic, hit "New Topic" and you'll get a blank page, with space to put your subject and message. Once you've written what you want to say, press "Submit" at the bottom of the page.
Replying to a topic
To reply to a topic, enter it so you can see everyone's comments. The buttons at the top right will now say "Reply", "Subscribe" etc. You can either press "Reply" which will give you the same blank screen as "New Topic" above, or you can scroll to the bottom of the topic page, past the comments, to the "Quick Reply" box. Type your message in there and hit "Submit" or "Submit Quick Reply" depending on which option you've gone for.
Hopefully this will help people with using the forum.