You can easily edit your booking from your dashboard.
Go to "List View" on your left hand sidebar:
You can view all your bookings here by selecting the date range you'd like to view.
You can also search for a booking by booking reference, event name, vehicle plate etc.
Once you've found the booking you'd like to edit, select it and the option to edit will be in the upper right hand corner in a green box.
You can now go through your booking making any changes you need.