How do I adjust the head support height?

Before adjusting, have your child lean forward slightly. Squeeze the red adjustment button on top of the seat and pull the back support up until it snaps into one of the 6 height positions. To lower it, squeeze the red adjustment button and push down. Check that it is securely snapped into one of the 6 positions by pulling up on the head support. The bottom of the headrest should be even with the top of your child's shoulders, and the shoulder belt must be positioned in the red zone.