In StoreFront 6, the Shipping page is the first page of the checkout process after signing in or creating an account. By default, the Shipping page displays empty shipping address fields, even if you are a returning customer and have already defined an address.
The Select Address Mod is small bit of code that you add to the Shipping page to fill in the address fields with the first address in the address book (if there is one).
Instructions
Follow the instructions in this document to install the modification: Select Address Mod
Click here to visit the add on creators homepage