You can setup appointment reminders on an individual basis for each client.

If you go into each client that has authorized you to send reminders, you can edit their email address, and underneath that, select to remind 1, 2, or 3 days in advance. (It will be ~25, 48, or 72 hours in advance)


This will go into effect for all appointments, even if they were scheduled already! (but only for appointments in the future.

You may want to create a test customer with your email address and create an appointment within 24 hours from now to see how the emails look, and confirm that they are working.