To cancel an appointment, 

1. You will have to log in. Navigate to the top-right corner of your screen. If you are using a desktop computer you will click on your name in the top-right corner to find the login screen. For mobile users please click the menu icon (three horizontal lines)
2. The login screen will ask you to enter the username as in your email ID and password. This should be one which you had setup at the time of enrollment. If you have not enrolled before, feel free to reference the enrollment guide here
3. Once logged in, you will see your name on the top right corner. Next to it will be a drop down arrow
4. Click on the drop down arrow and select Manage Appointments
5. Under Upcoming Appointments, you will see the option to cancel your appointment