After choosing the service the customer should also select an employee for it.
In the list there are all available employees for each selected service.
If the customer makes an appointment for the first time and doesn't know the employees he /she can choose any of them.
For each employee you can define whether he has general or individual working hours and add a vacation or sick leaves.
More information about it you can find here: Employees: new fields
Good to know: it should be allowed for the employee to be shown on the public booking page. You can define it in the admin area under Employees -> Edit an employees -> Restrictions
After that the only thing left is to select the date and the time for this appointment. The customer can select any month,day and a time slot.
Good to know: You can define the time intervals under Settings -> Booking in the admin area.
More information about Booking Setting you can find here: Booking Settings