Content is currently under development for Vendors / Supply Chain. When complete you will see a list of all the different documentation sections here that you can go to, including vendor management, purchase orders, receive vouchers, reports, business inteligence, 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.