You need to go on the Tesse platform and choose the course that you are interested to join.
Every lesson of the live course is already scheduled by the instructor. While you choose the course make sure that you can join the lesson in due course. When the course starts just press the button play to join.
Tesse gives you an opportunity to interact with the instructor in the real time. You may use live chat to type all questions that come to your mind. You can also use a special button to ask live voice question. You can speak after instructor approves your request.
It depends on the course you choose. You may find both paid and free live courses on the platform. Once you pay for the course you will access all of the prepared lessons.