After you have created a forum, you can create topics.
(1) Open the forum.
(2) Now, you see the title and the description of the forum as well as a list of already existing topics.
(3) Below the list of topics, you see an input mask.
(4) Insert a title and a text.
(5) Click on "preview >>".
(a) If you want to change anything, click on "edit".
(b) If you are satisfied with the preview, click on "publish