Navigate to Schedule top tab > Courses side tab > Click on Options > Add > In the dialog window (shown in screenshot) search for the course > select the course > click OK
Finding a Course Code
You can search for a course using the "CrsNo" Column.
If you click on CrsNo column name, then you will be able to search on that column.
If you still do not find the course, then please search based on the Description.
If you still do not find the course you are looking for, please submit a help ticket.