Contract an electrician to wire a power supply to the louvered attic vent. If a power supply is not readily available, this step may involve running a circuit from the circuit breaker box.
Cut two 2-inch-by-4-inch boards to span the distance between the vertical studs on either side of the louvered attic vent.
Nail a 2-inch-by-4-inch board to the vertical studs above the louvered attic vent. Measure the height of the gable fan and nail another 2-inch-by-4-inch board to the vertical studs at the appropriate distance below the top board.
Screw the gable fan to the 2-inch-by-4-inch boards attached to the vertical studs above and below the louvered attic vent.
Switch the circuit breaker to the fan off to prevent electrical hazards while connecting the fan.
Mount the thermostat control box for the gable fan to a vertical stud below the louvered attic vent. Connect the gable fan wiring to the thermostat box with wire connectors, according to the manufacturer's instructions.
Connect the thermostat control box wiring to the power supply with wire connectors, according to the manufacturer's instructions (e.g., black to black wires, white to white wires).
Switch the circuit breaker to the fan on. The attic gable fan should switch on if the attic is warm, and switch off when the attic has cooled sufficiently.