We have done it several times at Capt Cooks, usually breakfast. It is really easy. When you come into the restaurant they have a posted menu overhead.
You approach a tv screen (there are 3) then you touch on the picture of the item you wish to order. Sometimes there is a cm standing by if you need help. Once you have finished your order you will recieve a receipt.
I think you will need to make your order then talk to the cm who gives you the food if you for example want to have no lettuce on your burger. So complete your order and immediately go over to the food area and talk to the cms behind the counter about your special requests.
They also have a refrigerator to the side filled with drinks, yogert, fruit, sushi, alcohol and select sandwiches/salads for to go. There is also a display case with muffins, danishes, cup cakes and cookies. Neither of these items will require use of the touch screens. Pick up what you want and then head to the register with these items and your receipt. You pay, they will give you a pager and you later come pick up the food ordered from the touch screens.