Air France has their own frequent flyer program called “Flying Blue”. Sign up for their program here. When you sign up it says
To earn Miles, always provide this number when reserving tickets or checking in.
All the Flying Blue information will be sent to you by email.
You will receive a bonus of 1,000 Miles after you have received your first account statement by email.
Next, go to this questionaire for an additional 1000 miles. I always credit miles flown on Air France to my Delta account, however, Air France is considering merging with Delta / Northwest which makes this short promotion worthwhile.