2000 Windstar radiator cap

I can't seem to find the radiator cap on my 200 windstar, was going to change the antifreeze and am not able to find the cap, someone mentioned that you fill it thru the reservoir tank and just drain from lower drain plug, any one know the procedure or if there is a radiator cap.

There is no cap directly on the radiator; you're looking for the cap on the reservoir (which is on the passenger side of the engine compartment).