How to create a class schedule
A schedule is one occurrence (or a repeating series) on the calendar.
Steps
Go to Classes → Calendar
Click a time slot or New Class Schedule
Select class and trainer
Set date, time, and duration
Optional: location, notes, difficulty, repeat (daily/weekly + end date)
Save
Also
View Classes → View Classes → Action → View Class Schedule for one class
To remove a schedule, open it from the calendar or schedule list and delete (only when safe for existing bookings). Steps to modify or delete a schedule
Go to Classes → View Classes
Choose the class and click View Class Schedule from the Action column
From the schedule list, you can:
Edit Schedule (allows editing trainer and end date)
Delete Schedule

How to change the trainer for a class?
Changing trainers for an individual class is not possible. To change the trainer for the entire class schedule, goto Classes → View Classes → Action → View Class Schedule → Action → Edit Class Schedule
Related
How to book members into a class
How to book an enquiry for a trial class