Install course app in Administration > AppStore. After this you will find courses in the calendar (cog menu top of the page). Before you create a course you need to create the classes you want to link to a course. After that you go to create your courses and their details by cklickin the plus icon top of the page. Return back to admin calendar to link the classes to the course. The classes must be liked one by one. The courses time span shifts when you link new classes to a course. A course needs to be created and completed at once as you cannot change the course details after there are bookings on a course.