How do I properly secure my child in the car seat?

Place the harness straps over the child's shoulders and buckle them (you will hear a click). Buckle the chest clip and pull all slack out from around the waist by pulling up on the harness strap while pushing the chest clip down on both sides. Tighten the harness by pulling the harness adjustment strap until you cannot pinch any harness webbing at the child's shoulder. Finally, raise the chest clip to the child's armpit level. The harness is tight enough when it lies in a relatively straight line without sagging and does not press on the child's flesh. (Pages 51-53)