This is set in Appointment Types. Toggle 'Allow Individual Coaching Rates' to set a split per coach.
Go to 'Appointment Types' from main menu.
Click add new (pink plus button)
Enter name and duration. Description, tax and color is optional
toggle 'Allow Individual Coaching Rates' to on. This will show the 'Rates' table.
Add new rate (pink plus button)
Select Staff Member
Input Cost Per Session which is what you will charge the member.
Input Pay Rate Percentage which is the percent split the coach will get.
Hit Save, and repeat for additional coaches.
Note: If you allow for 'Individual Coach Rates', only coaches with a rate set, will show up for that appointment type. When creating an appointment, and a coach is not coming up, make sure they have their individual rate set.