Hi Bruce,
Shipping through the POS isn’t an area of our expertise. We do, however, provide a very solid integration to ShipWorks, which is a great solution for managing shipments, label printing, etc.
You can learn more here: http://www.shipworks.com/
And you can find instructions on how to use it with your NitroSell webstore here: Seamlessly Shipping Your Orders by Leveraging our ShipWorks Integration
Regards,
Donogh