First, access the seat panel at View Orders > Detailed. Your panel may look differently from the picture below due to hall specifics.
Quick Tip: once on the Orders Panel, bookmark the address displayed on your browser’s address bar. You can use that same URL to access the panels directly, saving time.
Click on the seat you would like to move, the seat detail dialog will be displayed. Then click on the seat name, on the upper left corner of the dialog window.
The dialog window disappears and the available seats are shown. Unavailable seats will be grayed out and unselectable. Just select a new free seat and the change will be automatically made.
Once you choose a new seat, the seat details dialog window reappears, confirming you have made the switch.
All of the orders associated with a seat are moved to another one with this process, so if a player has multiple orders, all of them will be moved together.