The idea with the delivery of the digital goods is that you will modify the order history page for the details. On this page you will need to add link for the item and apply the download server behavior. We have a guide on creating on delivering digital goods but it is not specific to PowerStore. It covers the steps that would be taken on an order history page to allow download of digital goods. Here is a link:
If you have an understanding of how the download server behavior works and should be configured this part will make much more sense.