You cannot unpublish a course once it is published. If you are a paid Versal user, you can set the course view to private in order to hide it.
You can remove a course completely by deleting it. This is a permanent action and cannot be reversed. You will lose all course content.
First, go to the "creating" section in the left sidebar. Next, in the course list select the checkbox or boxes next to the course(s) you want to delete. The delete button will become active. Select the button to delete the course. You may select more than one course at a time.
You can also delete a course from the "all courses" list by clicking the "..." icon on the far right. Then, select "delete".