How do I convert the 5-point harness to a 3-point harness?

To convert to a 3-point harness, unlock the buckle on the harness. When changing harness strap slots, make sure the harness straps are going through the same slots in the seat pad and seat back, and the straps must go into the slot that is even with or slightly above the shoulders, avoiding twisting. (Pages 16-17)