Switch on the flashlight. Turn off the power to the home at the main breaker. Confirm the power is off. There should be no power in the home at all.
Loosen the four screws that secure the distribution panel cover and remove the cover. Do not remove the cover for the main breaker.
Locate two empty slots in the electrical panel for the 240 volt GFCI breaker.
Flip the breaker's switch to the off position.
Insert the breaker into the two available slots tilted slightly towards the center of the panel, until the back is secured. Push down on the front of the breaker, until it locks in place.