This is unlocked at the very start of the game during the Prologue. You will start by pushing a cart with a man ( Your dad or grandpa ? ) on it, keep going until you get to platform where you have to pull a lever to continue. Before proceeding, go to your right down the path which leads to a beach. There will be a pile of rocks you must interact with. Hold
- (depending on whichever brother you want) , Achievement will unlock once you start chucking the rocks in the ocean.