http://us.playstation.com/digitalupgrade/
TO DOWNLOAD PS4™ VERSION OF GAME:
Step 1: On your PS4™ system, register the PS4™ system with the SEN account through which you redeemed the Code.
Step 2: Select the PlayStation®Store icon on the PS4™ system home screen.
Step 3: Search for the name of the game on PlayStation®Store and select ‘Purchase’ to download digital version of the same game to your PS4™ system hard drive. The discounted price will be deducted from your network wallet according to the Terms of Service and User Agreement.
Step 4: Insert the PS3™ game disc into your PS4™ system**.
**
PS3™ game disc required to play digital version of the game on your PS4™ system.