I am going to guess that you have two separate cables comming from the rear and need to connect them to a single cable. I had a similar problem and found a quick fix. I used a hand brake lever and ran a cable around back through the firewall to the back of the brake pedal. This does two things, it works all four wheels and gives you a way to control the brakes with your hand while you use your feet for the gas and clutch.

otherwise you will need to makeup some kind of connection between the three cables.