2010 Dodge Caravan - Overheating

hi, i have a grand caravan 2010 cargo,
i have a problem cooler, i try find where they losse the liquid prestone,but i can t find, is not gasket motor, because my oil the color is perfect, and i have no white smoke muffler,
someone have alredy this problem?

How often do you add fluid? How much do you add?