When an appointment is deleted, it's deleted for good and cannot be retrieved.
Appointments can only be deleted after they've been canceled.
Once you've canceled an appointment, it will no longer show on your Appointment Calendar. You can find a canceled appointment by either going to the individual client record in your Client List or by filtering an Appointment Report to show All canceled appointments.
Select the canceled appointment you want to delete, then choose Delete, type "Delete", and click OK. Appointments need to be deleted one at a time and cannot be deleted in bulk.