After you’ve been active on the forum for a few hours you’ll be able to interact with the guild page, where you can introduce yourself to your new guildmates and discover what it means to be a Thornmouth. The leadership roster will tell you your guild leaders as well as who takes care of what around the forum. There is also a Q&A for any further questions you may have.
Don’t worry about not knowing how to navigate a forum, I was new to it when I started too. You’re always welcome to just lurk around and see how things work or dive right into discussion, whatever you’re comfortable with.