My car is overheating and I can't find out why?

I bought an old 96 Honda Civic from a friend and it's been sitting for while. It's been started every month or two. He told me it runs and drives but overheats and he can't find out why. I've changed the thermostat and the radiator and after the car warms up for a bit it still overheats and coolant even boils in the overflow tank. Also white smoke comes from the exhaust manifold area.

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