Under "Schedule" page, click on the "Add New Schedule" button:
Choose on the "Create" button against the Flexible schedule option:
***Note: You can only use one schedule type per service (you can choose between a fixed time or a flexible time schedule for each service)***
This would then allow you to choose on the employee (click on the "Choose" button against the employee you want to assign the schedule to):
Upon choosing the employee, this would then allow you to set up your available times either for a recurring schedule or a fixed times/dates:
When you are done with adding your available times, this would then allow you to set any buffer times for your schedule (you can either choose between taking back to back appointments or setting up buffer times for the schedule):
Click on the next page, where you can select/deselect which service/s this schedule would be associated with:
Make sure to click on the "Finish" button on the right hand side of the page to save any changes.