After a reservation has been submitted, changing it requires that you "Request Changes" from the renter organization.
Go to your reservation's detail page (If you don't see your reservations, see the support article: Where Are My Reservations?).
On the reservation detail page you will find a "Request Changes" button.
When you click on Request Changes, you will be able to enter in detail what changes you want to request. Describe the specific changes and click Submit.
Your request will be sent to the district for review and approval. Your request also will be recorded in the Comments section at the bottom of the page. If the request is approved an update will be made.