Switch off your garage’s breaker. Remove the old fixtures. Use a screwdriver and hammer to knock out holes. Plumb the wiring through and lift the light into place. Attach wires accordingly: black to black, white to white, green to green. If screws are present, attach one screw to one side of the strip and align the light so that it’s parallel to the garage’s layout. Screw in the remaining screw(s). Flip the breaker back on.