Remove the bolts from the valve cover and lift it off. Remove ALL the old gasket material from the valve cover and the engine using a scraper such as a razor blade ( be careful not to drop any down in the engine) install the new gasket and the valve cover. Tighten the bolts firmly but not TOO tight because you can break one off in the head of the engine and that is a real problem. The auto parts store will have the torque value of the bolts and you should buy or borrow a torque wrench to get the bolts tightened properly.
