If you can't see any courses linked to your departments in School > School Structure > Departments, you need to make sure the start date is current. If you need to set up Departments, follow this article.
If you put a start date for the future, it won't appear anywhere until that date. For example, if you set the start date to 1st September, the course will appear under the Linked Courses section on 1st September, not before.
Using a future date
When using a future start date:
Mathematics is not showing under the Linked Courses section:
Adding a start date
When adding a start date that is current or in the past:
Mathematics appears in the Linked Courses section: