Just before getting out of the house and into the yard, make sure you get the keys from the hand of the dead body in one of the rooms by the exit.
Go outside and to the garage. Open the door using the keys. Inside, in an alcove, is a green ladder. Pick it up, go outside, and to the back of the garage, where you'll find some scaffolding.
Use the green ladder you're carrying just above the yellow ladder on the scaffolding. Then climb up to the top. Stand on the scaffolding for a few seconds, and the achievement will unlock!