A coach's pay rate can be set on their profile. Go to: Staff > View Staff > Manage Staff Member > Edit Staff Info > View/Modify/Add Staff Member Pay Rate
These pay rates are per class, and will be reflected in the payroll report (Income Reports > Coached Classes (Payroll)).
If a coach receives a different pay rate for different classes, you can override individual class pay rates by navigating to:
Schedule/Classes > Class Types > either select a previously created class type or create a new class type > under "Coach Payment Override" enter the amount your coaches will be paid for this class (if different from their standard pay rate).
Please note that class types with "coach payment override" filled out will appear on the payroll report as "Specialty Classes."