To install a ground fault circuit interrupter circuit breaker, first turn off the main breaker before placing the breaker in the panel. Connect the neutral wires before connecting the hot wires. Turn the power on to test the breaker.
After turning off the main breaker, put the GFCI breaker into the slot in the panel so the locking tab on the back of the breaker attaches to the bus bar. Connect the white pigtail wire from the GFCI breaker to the panel's neutral bus. It should be secured to the terminal side of the GFCI breaker, which is indicated by a white dot. Connect the black or red hot wire from the panel to the GFCI breaker.
Turn on the main breaker, and then activate the GFCI breaker. If the breaker holds, push the test button. If it clicks and moves to the center tripped location, the ground fault features are working appropriately. If it trips, take the wires away from the circuit one by one until it stops tripping and stays on.
GFCI breakers trip for several reasons. Wet connections or conduits can cause a trip, as can shorted wires or wires with a lack of insulation. Neutral wires coming in contact with ground connections can also cause a breaker to trip. Any trip necessitates a reset of the breaker; reset it by turning it off, and then turning it on again. A properly working breaker stays on when reset.