Hi,
Better late than never
Your question seems more to be related to PrintShop Mail Design than PrintShop Mail Web.
In PSM Design version 7, you can insert a barcode object and set its 'Type' property to USPS OneCode.
PSM doesn't pose any constraints on the value of the barcode, so if you are looking for standards/norms, you might want to contact the organization that will be using the barcode and ask them about what information to include.
Also note that the USPS OneCode object lets you specify such parameters as the quiet zone andcheck digit method.
Hope this helps!
Benoit