You will need a 3/8 allen key, a pan to drain the old fluid into, 2 litres of either Auto transfluid or manual gear oil (personal preferance) I prefer Castrol Transmax Z but it's expensive so just use ATF, maybe with a Nulon G10 (I think thats the name) additive. With the car level undo the lower allen key bolt on the drivers side of the gear box roughly in the middle, leave it to drain. Replace the allen bolt and do up to roughly 35 Nm (tight).
Now undo the top allen key bolt which is about 10 cms up from the lower one, than improvise to make some kind of filler, I use a clean piece of garden hose with an upsidedown coke bottle on the end taped on with the bottom cut off the coke bottle. Now get someone to hold it up in the engine bay and pour in 2 litres of trans fluid or untill it starts to trickle out, making sure the car is level so as to not over fill. Replace allen key bolt and tighten. Done!