Hello @Bill119,
The guest should log on and click on "Trips", then find the reservation with you and click on "Change or cancel". They can then change the end date and submit the request. You must then accept it when you receive the notification.
Alternatively, you can initiate the process by clicking on "Host" and then on "Your reservations".
then find the reservation concerned and click on "Change or cancel" in that reservation. Then change the end date and submit the request. The guest must accept the change for it to bevome effective.
Steve.