The answer to 'how to fix GFCI outlet' is to reset the GFCI outlet if it has tripped. GFCI (Ground Fault Circuit Interrupter) outlets are designed to trip when they detect a ground fault, which can happen due to a problem with the outlet or the connected device. To reset a GFCI outlet, simply press the 'RESET' button on the outlet.
If the GFCI outlet continues to trip, there may be an issue with the wiring or a connected appliance. In this case, it's best to have a licensed electrician inspect the outlet and diagnose the problem.