2 Answers

Usually you can find a round container, shaped like a ball, with a black cap under the hood near the windshield washer container. It should be about half full of greenish antifreeze. To fill, simply unscrew the black cap when the engine is cold and add your antifreeze up to the full mark, it is hard to see, but half full is where the full mark is (at the seam). The antifreeze needs room to expand when it gets hot so dont fill it to the top. The hose on the bottom of that container goes to the engine and then to the radiator. NEVER take the cap off when the engine is hot. It could explode in your face. This works for all Golfs, New Beetles and Passats

http://wiki.answers.com/Q/How_to_fill_the_radiator_on_a_vw_passat

the washer bottle the radiator expansion tank through the leaking window seals