Have you ever taken a French class? If not, you should probably start by taking one. 
If you’re not interested in doing that, then you might try getting a copy of the textbook and reading a couple chapters at a time and doing the practice exercises.  
You’ll also probably want to watch a few movies or other media in French.
assitant
How about Spanish instead?  It’s just a bit easier to learn for a native English speaker.  Do you know what a foreign language is?
assistant
I want to learn a new language. Do you have any tips for getting started?
user
Which language are you thinking of learning?
assistant
French
user