How do I manually install the DLC?

[Famix]

I just got it from Humble Bundle, but instead of a steam key, it's a DRM free download

[Parcelyte]

Humble Bundle gives you the Steam key to both the main game and the DLC. Above the DRM-free downloads in the center there is a font "Redeem Steam Keys" or something. Just click on it and you will see both steam keys.

[Famix]

Thanks, man! Someone already told me how, but I'm keeping this up for people who skimmed through the page like me

[Bobby]

Extract both the Game and the Whistleblower DLC. Open the Whistelblower folder and select and copy the 'OLGame' folder and paste int into the Main Outlast game folder; example
C:\Users\Downloads\Outlast-DRMFree\Outlast
It wont overwrite anything but will creat another folder like this;
C:\Users\Downloads\Outlast-DRMFree\Outlast\OLGame\CookedPCConsoleDLC

When you next lanuch the game you will get the option to launch the Whistleblower DLC in the main menu.