Only users with a administrator or booking administrator role can edit a booking.
These users can edit their own bookings and the bookings of other users.
Click on a booking on the booking sheet, which will bring up the below overlay and then clicking the 'Edit booking' tab.
After clicking the 'Edit booking' tab, you will be taken to the edit booking page, as shown in the image below:
Here you can make changes to the booking. Once you have finished making your changes, click the 'Submit' tab. You will now be taken to the booking confirmation page with the new details in place: