YouTube should answer your question. Pretty sure you fill via the "level plug" until it just starts to dribble out. IIRC it's on the front of the g/box halfway up. Advice is to make sure you can undo that plug BEFORE draining the fluid. You need some sort of oil pump or pipe and funnel to fill, I have a Sealey manual big syringe thing, costs around £13 if you shop around, invaluable tool.