The client portal can be used to allow clients to request appointments with you or this feature can be disabled.
To disable this feature, go to your TheraNest portal settings: Organization > Client Portal > Settings.
To turn on self scheduling make sure that option is switched to turned on. You can also control when clients can schedule an appointment with you. If you don't want them to be able to schedule and appointment in less than 24 hours make sure that's turned off. You can also prevent them from canceling or rescheduling an appointment within 24 hours.
If you want to limit self scheduling to only certain clients, be sure to turn self-scheduling on but then off for certain clients.