How do I find the small key?

In the box, you will first make sure all pieces are slid all the way to the left. Slide the right half of the butterfly wing up next, and that should get you going.

If you are in a hidden object scene in the forest suite then the key is in a box on the shelf that has a puzzle lock. Its a simple puzzle though.

Check the guide for Find the Small key in the Forest Suite if you can't find it.