Babies
Newborns only see high contrasts. Place the cards with the letter side in the box for visual stimulation and brain development. As your baby's vision develops, he will become interested in more complex patterns and you can place the cards the other way around.
Toddlers
Make it a fun game. Name the letters and try to name an animal with the letter. Then turn the card over and name the animal. What sound does the animal make?