Instructor availability can be managed by account Admins and Owners, or by the instructors themselves with the new Appointments scheduling feature.
Please note that instructors don't need any additional permissions to manage their availability, they just need to be set up as staff member with the instructor status*.
*If you're yet to create staff accounts for your instructors, see Creating instructors.
Instructors can manage their availability by heading to My Account >> 'Manage Appointment Availability'. On the next page, they'll be able to manage their availability.
If you're an account Owner or Admin and are looking to manage your instructors' availability yourself, please see Managing instructor availability for Appointments.