Unfasten the harness shoulder straps so that the two short straps dangle from the seat backrest. Insert your hand under the seat back cover by undoing the velcro on the underside of the seat and access the buckle on the back of the seat back. Thread the buckle from the seat back through to the front. Reposition the strap to the desired position and replace by reversing the removal procedure. Re attach the harness for use and adjust the strap length to suit the child.