I updated the schematic specific to your mower (14.2V). You will need to procure a 25A 200V Full-wave Rectifier Bridge to convert the AC output from the alternator stator winding to DC. This is wired between the stator winding and the battery. All of the mower loads, including the lights and ignition, etc, must be connected downstream of the ignition switch. The regulator is built in two pieces, a hand-wired circuit board, the power resistor, and the NFET, which must be bolted to (but electrically insulated from) a large piece of metal.