When a drinks order is queued a number will appear next to the "Bar Orders" button.
Pressing on "Bar orders" will take you to the "Bar Orders" view where you can see the order.
To prevent anyone else from preparing the same order you can acknowledge the order by pressing on the work "Acknowledged" at the top of the ticket.
Once you have prepared the order press "Ready".
Finally once you have delivered the order to the customer, or it has been collected by waiting staff press "collected".
Once marked as collected, the order will disappear from the view.