What is the vaclum advance for on an engine and where does it go to on the carburetor?

I have vacuum advance on my distributor but the hose is not going to the carb. When I bought the car it was already like this and I want to connect it the way it should be. I have a 1978 Chevorlet Monte carlo V8, 305 with a 2 Barrell Carb. Which fitting on the carb does it go to? I know it's got to be one of the left front two but which one and where do the others lead to so i can make sure they are connected properly?????.