Managing your shipments is fairly easy once you get the hang of it. Click on the Delivery Trucks icon in the bottom menu for a clear picture of what you've ordered and what's ready to be served. When you want to order goods, click on the delivery truck icon and then click the yellow plus sign at the bottom of the window. That will sort the displays in the order of what goods are needed most.
You can also order more by clicking on the displays you need shipments for.
There is a limit to how many shipments you can order at once. The maximum number of trucks available is 40.