Transmission fluid - 94 Charade


I seem to be losing a bit (not much) of transmission fluid from the automatic gearbox bit so the gear changes get a bit abrupt. I was losing a lot apparently via oil seals which I learned on here was a known problem, and that more or less fixed it.

As you can tell, I know little of these things. I've managed to locate the dipstick but can't work out how to get more stuff in - what looks like the top of the reservoir has a couple of tubes coming out of it. Do I just unscrew it?

The dipstick shows two levels, one cold and one hot. At the moment, on a cold engine, it is right on the line of the cold marking. Is this OK or does it need topping up?

Many thanks...