To unlock and download the extra content please follow the steps below:
Enter the main menu of the game.
Click on your player avatar to the top left to enter the profile data menu
In the profile data menu, click the "Rewards" tab
Click the "Redeem code" button to the bottom right
A pop-up screen will appear: please enter your activation code
The game will ask for a restart to receive and download the Deep Ocean data via the Autopatcher.