To adjust the harness straps on the seat pull up on the ladder lock and down on the webbing to loosen the straps. To tighten, pull down on the slip ring. For a tighter fit, pinch the webbing and release from the back of the slip ring and pull down until snug.
To adjust the shoulder height position, detach the grey adjustment clip from the harness attachment loop. Reattach clip to the desired harness loop that fits best for your child.