The first requirement is to be a French national. Then you have
to undergo a series of exams either physical or theoretical. It is
usually required that you have the baccalauréat (the exam giving
access to university) to sit the exams, but police cadets can be
exempted. At the same time there is a vetting process (ckecking
about morality, existence of previous convictions or police
files,etc...). After all that, you will have to go through police
academy before entering your probation year.