the same way you start an engine that you used yesterday. However, if it doesn't start as it should, then you have to deal with whatever problem is preventing it from starting. I am going to assume the engine was in a car. I'd be surprised if the battery is any good at all, sitting this long, it's plates have probably sulfated so badly it isn't likely to take and hold a charge. If you do try to recharge it, make sure the cells are covered with DISTILLED WATER & try recharging at a very low rate, say from 2.5 to 6 amps. It may take 4-5 days to brake down the sulfates & recharge at this rate, but I doubt the battery will be any good, having set unattended this long, so I'd plan on a new one. If this puppy was rode hard, put up wet & none of the fluids were changed before storage, I'd begin with ALL new fluids. Brake fluid, Coolant, Engine oil, Re-lube the wheel bearings, Tyranny lube, Drain the gas tank & the fuel lines, if the old gas is still in there, ya gotta get rid of it. Refill the tank with fresh gas, with 0.4 oz per gallon of Marvel oil mixed in with the new petrol. After you run a tank or two through it, I'd change the fuel filter too. I'd remove the spark plugs & squirt about 4 tablespoons of Marvel Oil in each cylinder & let it