The blanket sign is like pulling a blanket up over your body. Make the blanket sign by taking both hands with your fingers extended and thumbs tucked under. Start with your palms facing your body and down low, then pull your hands up to chest level.
When you tuck your baby in at night, make the blanket sign. "Here is your blanket."
If your baby has a favorite blanket, she will be highly motivated to learn the sign. You can use the flash card to help her generalize the sign and learn that it applies to all blankets, not just hers.