From your 'My Hub' page (please see below)
On the left hand side of your account, you will see the side menu in which you can select 'Calender'.
This will then show your calendar with any booked session/events...
You can simply select the activity and click the activity name to 'View' which will then show all the details for that specific activity
If you then hit the 3 horizontal grey dots next to the 'Event Description' you will have the option to cancel or edit the event.