How is the evaporation of water from the ocean related to the formation a hurricane?

Evaporation leads to condensation, which gives you your convective cloud formation. As hot moist air rises and condenses, more air must move in underneath to replace the surface air that was lifted. With this process being conducted over several hundreds of square miles, air pressure is lowered in the region, and rotation may commence thanks to the earth's coriolis effect. With rotation beginning and hot moist air constantly rising and condensing into convection, air pressure remains low and can continue dropping if water temperatures are high enough to support continued convection firing. The systems rotation speed increases, and you now have a baby hurricane, known as a tropical depression.