To install the Killzone Shadow Fall for PS4 you need to own a copy of the game. Download the full open week trial client which will include single player component. The maps are not playable is a standalone format.
From your PlayStation 4, access the PSN. The DLC is region-specific and will match only with the copy of the same region for which you are downloading the map pack.
From the PSN you will be easily sent to the PlayStation Store of your region. To download the DLC map pack, be sure of downloading it from PSN account which is of the region that matches with the region of your copy of Killzone Shadow Fall.
Here are the region codes for Killzone Shadow Fall for your reference:
- CUSA-00002: Europe
- CUSA-00008: UK
- CUSA-00065: Asia
- CUSA-00085: Japan
- CUSA-00190: US
- CUSA-00191: Latin America
After downloading the DLC map pack you are free to play the game from any PSN account on the console on which you have downloaded the game.