This achievement has several parts to it. First, you must find the 5 Torn pages throughout the various levels of the game:
1. Traverse Town - Rewards from rescuing 51 Dalmatians from chests:
2. Agrabah - Dark chamber in the lower portion of Cave of Wonders
3. Monstro - Chest in Chamber 6, high in the air (High Jump & Glide make this easier to get)
4. Halloween Town - Examine the book shelf in Dr. Finkelstein's Lab
5. Atlantica - Chest above the blue trident thing in Ariel's Grotto
Once you have all of them, you can go to Merlin's house in Traverse Town and examine the book on a desk to go into the 100 acre woods area. At the beginning, on 1 area will be visible. Each area needs to be completed (you'll get a notification that a torn page became a new item each time you leave an area after completing it) before the next will become available. Each has some kind of mini-game that you'll need to play, though none are terribly difficult. Once you finish the 5th area, you'll get a cutscene and the achievement.
Below is a video of the area. I did not create the video, and all credits go to its original creator: