There are formalities that companies have to complete when hiring foreign labour for a job in France.
You can complete all the formalities beforehand at the French Consulate or the French Embassy in the country of the company in question.
All the formalities are explained on the official French website:
Accueil | Étrangers en France (interieur.gouv.fr)
You will find the following options:
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.