This has been unlocking normally from challenges done in multiplayer mode, and you may get it without even trying. Find the Abstergo Story option in the menu. You will see various square pictures with blue icons below. Those icons represent challenges. Highlight the second set called Abstergo Dev Diary 1_Hack. You must complete two challenges to unlock it. Highlight the blue icons and see your progress. You need to earn a Multi Kill Bonus in any Team Mode or Wolfpack. This is easily done in Wolfpack with a second person, as both targets stand next to each other. The other challenge is to get Aerial Kill Bonus (20 total). After you get both challenges completed, you will unlock the video and the achievement will unlock without you having to actually view the video.