How To Install A GFCI Outlet With 4 Wires, with a ground wire. I wanted to show a quick video showing anyone how to correctly wire a GFCI outlet. Usually when you have 4 wires hooked up to a GFCI outlet, it is because that GFCI is protecting another outlet on that circuit. There should be two sets of hot and neutral wires. The set that brings the power into the box is considered the LINE. The set going to the other outlet is the LOAD.