If the start time for your hearing has changed but is on the same day as your approved reservation, you don't need to do anything. Just dial in at the new time and your reservation will work without any modifications.
If the date of your hearing has changed, you need to make a new reservation. On the right side of the screen, follow the four steps to make a reservation for your new hearing date. You can cancel your old reservation by clicking the trash can next to your prior reservation.