How Does The Heart Help The Lungs Do Its Job?

The heart receives "used" blood, after a cycle around the body via the pulmonary artery (which is really a vein).  There the blood is re-oxygenated, and sent through the arteries to to capillaries to the arterioles to oxygenate organs, then goes into venules, then veins then back to the heart to be re-oxyenated again to do the whole trip over again.  If you mean how does the heart help the lungs help us breathe, it's another set of organs that receive blood via the massive highway of blood vessels, and is part of our "waste  management system."
The lungs take in oxygen and give out carbon dioxide, a waste product, just like urine or feces, but nicer to deal with.