The forum activity allows students and teachers to exchange ideas by posting comments as part of a ‘thread’. Files such as images and media maybe included in forum posts. The teacher can choose to rate forum posts and it is also possible to give students permission to rate each others’ posts.
Note: The News forum in a new Moodle course is just for teachers to post announcements. It is NOT a discussion forum for students.
To add a forum you should turn on the editing and select it from the Activity chooser
I didn’t find the right solution from the internet.