How do you install an electronic trailer brake controller in a 1995 GMC Suburban 1500?

A brake controller has 4 wires on it, Black, white, blue,red.

Black is positive battery 12 volts connect to 30 amp circuit breaker to the battery

White goes to good solid ground

red connects to white wire from the brake switch

blue wire connects to 7 way trailer connector at rear of truck. If the truck has trailer package you will find the blue wire and red wires under brake booster taped to the harness you can connect your blue brake control wire to that blue wire. At the rear of the truck the other end of the blue wire will be taped to a harness under the rear of the truck. you will have to now connect the blue wire to the blue input on your 7 way connector

You can go to your parts store and tell them what the make of your vehicle is and they will send you a brake controller that plugs in under the dash near the floor where your left foot generally sits on the floor. Just above there is a place where it plugs in. They are very easy to install. The parts store people will show you where it goes. Nothing to it.