Our "forums" also are called "Groups": They're forums with membership features. (For one, Group members are notified of new activity in the Group.) Most forums are completely open to reading and posting by all, but some may have Group membership requirements.
Search or browse the Groups to find a forum in your area of interest. Chances are there's one already active and rolling. PRO and PRO PLUS members may create and own new Groups, should they have the need.