How do I adjust the headrest and harness height on the Graco Slimfit 3-in-1?

Squeeze the adjustment handle at the top of the headrest and slide it up or down to the appropriate position. The 10-position No-Rethread Simply Safe Adjust Harness System allows the headrest and harness to adjust together with one hand. For rear-facing, ensure straps are at or below shoulders; for forward-facing, ensure they are at or above shoulders.