How do I change the reservation for an activity?

Go to My Reservations from the profile drop-down in the site header. Hover over the 'Reserved' button and click to 'Cancel' the reservation. If other reservation dates and times are available for immediate reservation, these will show as 'Reserve' in yellow for that activity. However, if you do not reserve an available new reservation date and time for that activity immediately after cancelling, the original reservation will be held by the system.