You need a uPlay account to activate the CD Key Code for Assassins Creed 4 Black Flag Blackbeards Wrath. Simply log into uPlay and activate the code there. You can download the client here.
A Assassins Creed 4 Black Flag Blackbeards Wrath key for the UPlay-Client does not expire and after activation Assassins Creed 4 Black Flag Blackbeards Wrath can be downloaded and played forever.