There is no special setup or program that is needed to handle Purchase Orders. All you need to do is check the box on the Payment setup screen in the back office. Once that is done there will be an option in the Payment box of the shopping cart to select Purchase Order as the method of payment. On the billing screen of the shopping cart there will be a box for them to enter the Purchase order number. The Thankyou screen and receipt will show that a Purchase Order was used as the payment method and the number will be stared out.
In the backoffice of the store the order will show
Payment type: Purchase Order
Purchase Order Number: 12345 (where 12345 is the purchase order # they entered)
How you set someone up to be able to use purchase orders (authorize) and how you handle them after one is received is not done in ShopSite and would have to be setup by you. ShopSite will not automatically bill for a purchase made using a purchase order.
As far as your test order not showing up and the email not being received check and make sure you used a valid email (I mistyped mine when I was testing it on my store and didn't get the email
) Also see if you get and order if you enable and use the COD method.