You need to register the  tool which would involve going to Settings/ About / and retrieving register password (and be within the free update period )

You need to e mail support with your desire to have the French Language Authorized and get e-mail confirmation language is changed and instructions on how to proceed which I beleive requires deleting the existing software or doing a factory reset or something, then re-downloading all the software in the French language which will take all day with a high speed internet connection.