To edit a (timetable) Class Reservation, the Timetabled Class Reservation will first need to be created (see How do I create a (Timetable) Class Reservation?). Locate the reservation on the Booking Screen and tap on it
From here you can Edit the following:
The system will then ask if you would like to update all future reservations. Select NO or YES accordingly
For other changes to an existing Timetable/Class Reservation see;
How do I move a Reservation?
How do I create a (Timetable) Class Reservation?
How do I manage Customers in a Class Reservation?