Once you first complete the tutorial section you will wake on an abandoned alley with little to no memories of what happened.

After that you will receive a message from your mother, ignore it and equip your mobile device in the fourth slot (you must buy the secret paid DLC Andreas released on his private Whatsapp group).
Here is the link

Don't you ever turn on your flashlight, otherwise the device will heat up and you won't be able to install Whatsapp and you'll brick your phone.

Make sure you always grab your phone with your left hand.

You must complete the campaign on Nightmare mode while ignoring every single enemy in the game. Then, at the Doctor bossfight you must kill him using melee weapons (avoid using the knife, it's bugged and it won't work)

After completing the campaign you will get an unlockable called "Whatsapp.exe"

Now you can start a new game on whichever difficulty.

Realize your mobile device doesn't support Whatsapp

of Fear