To edit both the schedule and information for a reservation, find and open the reservation.
Tap the icon in the upper-right corner, then select Edit reservation.
If you want to change the schedule, tap the calendar until you get the new schedule. Be aware that by changing the schedule, selected items might end up booked. Every time you change the schedule, take a look at the item list; if one or more items are marked as booked, you might want to either replace the booked items with other items or adjust the schedule.
You can also change the list of items and other reservation information. However, if you're editing an appointment that is part of a repeating reservation, changes to the item list or information will apply to all appointments in the recurring reservation series.