Here is a typical Check-out process.

First go to the right side panel of the Reservation Manager, where today’s checking-in, checking-out and staying over reservations are listed in three different sections. Click on the reservation ID that you are checking-in, to bring up the Reservation Details window.

At the Reservation Details, go to the Check-In/Out tab, click on the Check-out button.

At the Reservation Details, go to the Check-In/Out tab, click on the Check-out button.

After a successful check-out, the reservation button in the Reservation Manager will appear red