Using actual windshield washer fluid is important as plain water won't be able to cut through the dirt, grime, and bugs effectively, leaving a smeared mess, which can be dangerous. Typically there is a translucent container to hold the washer fluid. Don' get it confused with the coolant container, which may look similar. If in doubt, check your owner's manual for the proper location. Fill the container with the appropriate washer fluid to the full mark. In climates that experience wide temperature changes season to season, make sure to use a washer fluid with anti-freeze properties during the winter months to ensure your washer system continues to function.