add salt (that goes into a hole in the bottom of the washer) and also a liquid rinse for dishwashers (picture of a shiny glass on the bottle, there will be a hole near the tablet place usually where you top up the liquid) that will stop the glass becoming white....

You'll probably notice there is a red light on somewhere on the washer... it should go off as soon as you top up the above...

You are probably out of the French equivelant of Jet Dry (Rinse Agent).  Most likely there is a small place to refill it by where you put the dishwasher soap.  Depending on how often you wash it should be refilled every 1-3 months.

If you use 3-in1 or all-in-one tablets, you shouldn't have to use salt nor rinse agent. They are only for powder "soap" (can you even get that, anymore?) or if your water is hard. Using too much rinse might leave a blue film.

I found that liquid soap works really well. Not least, because I can dose it as to how much I think it needs for a particular wash. Some tablets are pretty caustic and will slowly eat away at glass (giving the permanent white film on glass), so I reserve them for heavy duty.