Content is currently under development for Orders help. When complete you will see a list of all the different account documentation sections here that you can go to, inlcuding orders management, creating an in-house order, reports fulfillment queues, drop ship, and much more. You will also be able to select these from the menu on top.
In the interim, many of the options, fields, and selection lists have context sensitive help that you can view by holding your mouse over the item.