Eligible cards sold by participating retailers will include a voucher that you can redeem on the website for a digital copy of the game.
Oddly enough, the offer is valid exclusively for the Radeon R9 Fury. AMD probably has its reasons for this but it's quite a bummer for PC enthusiasts as folks looking to buy the more expensive Radeon R9 Nano or Radeon R9 Fury X do not qualify for this promotion.