The client or therapist can book sessions online. These can be set calendar times, requested times, or using your own developed template based on weekly times etc. Booking is very easy once you have regostered on the system for both you and the client. The therapist online calendar clearly indicates when  sessions are available or booked, and there are also a number of computer generated emails in the system to assist with setup and bookings.
 

A session is the time a therapist and a client arrange to connect and chat to each other on line. This session can be arranged by the therapist or the client. These session chats are totally secure behind firewalls and are only available at the time of the session to the therapist and client. Sessions can be Video, Audio, text chat, or a combination of them all using app to app or pc to app - or offline.
Go to the therapist, find a suitable available time, book it. Download the app, and at the session time, login and click on the session. It will open, and you will be with the therapist.