When you have an order selected, the "..." menu in the bottom left will have a new "Assign to room" option.
Clicking this button will display a list of checked-in guests, you may select a guest to assign the order to them. This will send the order to the guests booking. Clicking the "Get future guests" button will display guests who have not checked-in yet.
When you click the "pay" button on an order which is assigned to a guest, you will be given an option to "Charge to room". These orders will be charged to the room Beds24.