Go to the navigation bar and click on Orders > Order History. Click on the "In Progress" order that was delivered, and at the top select the Confirm order delivered button. This closes the order and changes its status to "Received". The items you ordered will be added to your inventory and entered costs will be updated on the item details, at the timestamp listed for the Delivery date.  You can chose a Delivery date or simply Confirm order delivered to use the current date/time.