After you have created a forum, you can create topics.

Procedure:

(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"