1. To redeem code go to: https://www.epicgames.com/account/code-redemptio
 2. Login or create new account (don't forget verify your email adress).
 3. Provide key and click button "Redeem Code". 
 4.  Game you can install and run using Epic Games Launcher

Fortnite is Epic Game’s new Action Building game. This Founder’s Pack includes “Save The World” a paid Early Access PvE campaign and the free Battle Royale PvP mode.

“Save The World” Campaign
The Storm came without warning and 98% of the world's population vanished … then came the monsters. You and up to four players lead the world's remaining Heroes in a battle to save survivors and hold back the monster hordes. Explore a large, destructible world where no two games are ever the same. Build huge forts, craft exotic weapons, find loot and level up your Heroes.

Minimal requirements: 

Processor: Core i3 2,4 GHz

Graphics: Intel HD 4000

Memory: 4 GB RAM

System: Windows 7/8/10 64-bit