You can perform the following actions over order in the Order monitor window: payment confirmation (Charge), payment cancellation (Refund), print the bill (Print receipt).
Right click on the desired order opens the order's context menu. You can select necessary actions in this menu.
You also can select several orders and perform action over the group of orders. Hold CTRL button and select orders via click on the order, or hold Shift button and select range of orders using up/down cursor keys. After selection of orders you can open context menu and select action.
There are check boxes on each row in action window and only selected orders will be performed by action (any of actions which is described below). If you don't want to perform an action on some orders in the list – just remove check mark on them before action performing.