The conversation will start right within your browser (Google Chrome or Firefox only), and you do not need to install any additional programs or plugins.
You can start a call by clicking on the link you get in the confirmation email, or by logging in to your account and going to your "appointments" tab, where you can see your upcoming meetings.
Click on "Start Call" and choose whether you want to have an audio or a video call.
Please note that you might need to grant your browser access to your mic and webcam the first time. If the access is denied, you can grant it by going to settings --> advanced --> site settings --> enable camera and mic.