There should be a small bolt (7mm Hex) and towards the back of the car (approx 20cm from the drain (7mm Hex) there should be a 17mm female hex. You will need to get some flexible hose to go up and over in order to fill. (I used an old garden sprayer (pump action), and some 3mm clear hose (from B&Q, garden sprayer also available from there)). Audi told me it required a "Special gravity Tool".
Hope this helps.