1: Go to Epicgames.com and sign in to your Epic account or register a new account.
2: Once logged in, follow this link to access product activation page. Enter your product key and press "redeem".
1: Download and install Epic Games Launcher on your PC. The link to official download page can be found here.
2: Open Epic Games Launcher on your PC and log in.
3: Once logged in, click on your profile name in the bottom-left corner and select "redeem code" from the menu. On the following page you will be able to enter your cd key and redeem the code.
That's it! Your game is now activated and you can find it in your Epic library. Head over there to download and play your game!