I'm told that that "ship now" link has been around for over a year, but it is a "beta" link of PayPal -- you can't get to it from your home "account overview" page either directly or from a chain of links. .... ...... ...... As I stated in my Guide, you can always make a label for a non-eBay transaction by going to that MultiOrder page (where you hit the Create button there), which I think maintains a history of your shipments.
Robert