There are 7 "worlds" in the game, each with 2 or 3 levels. Once you complete World 1's two levels and see the memory of the two kids meeting for the first time you "Can" get this Achievement.
I say "can" because you have to find it in the memory. While the memory plays you can move left or right to play the memory or rewind it. Keep playing through it until an object in the area shakes and makes a sound, once that happens freeze on that scene and a little box will appear and unlock the Achievement.
To unlock this, rewind until the door starts shaking and making sound, then freeze where you are until the door opens and the box appears. Below is a video for reference.