How do I properly install the car seat during booster mode with a back?

Remove the harness system and place the car seat forward-facing in vehicle’s back seat. Ensure the lap belt is snug and lies low across child's hips, routed behind the armrest in the green-labeled booster path. Secure shoulder belt snugly between child's neck and edge of shoulder without positioning under arm or over shoulder. Never use only a lap-only belt.