Make the course definition final when all the information has been filled in correctly. You can now make a request (offer/assignment) or course.

Note: You can only activate a course definition if there is at least one component linked to the course type.

That's how you do it:
Open the course definition and click on the 'General' tab.
Click on the 'Edit' button.
Change the status from 'Initial' to 'Definitive'.
Click on the 'Save' or 'Save & Back' button.