Depends on the circumstances. If the first flight was delayed because of weather, then no chances for compensation (although they may give you a few miles). The process is very straight forward, you just need to fill out the form on the AF website with all the necessary details and if applicable they will call you to confirm the address and will send you a check for an amount close to $700 dollars per passenger affected.
https://www.airfrance.fr/vlb/ecrm/FR...laintAction.do