I'm going through the process at the moment.
If you are UK qualified then you need just a copy of your qualification certificate and a copy of your statement of entry on to NMC register. These need to be translated by an approved translator (I'm just trying to get a reccomendation for a good one) and you take these to the DDASS of the departement you want to work in. The french do not use one national address and you are only allowed to register with one DDASS at a time so it's worth approaching the locations you want to work in first to see whether they would accept you first then you can apply to the correct DDASS for that location. Are you already in France or looking to move out there in the future?
I arrived in Paris in August as a newly qualified nurse so I didn't recieve my englich documents until November but touch wood it all seems very simple and straightforward now that I've managed to find out which office to apply to. I've had three interviews all in french and they've all offered me a post pending my reistration in france despite my french not being the best in the world so I think the job market for nurses here is quite good at the moment.
Hope this helps