How to join the Free Worlds?

I would like to join the Free Worlds, but I don't know how. Tried shooting down Navy ships, they became angry to me of course, but the Free Worlds didn't invited me to join. I really want to be part of this story.

Solution 1:

After 60 game days the southern militias and citizens formed the Free Worlds declared independence from the Republic, go to Free Worlds space (like the Rim) and visit the spaceports often. Sooner or later you will be given the choice of doing karate or putting your hands in the air. Choose the latter and don't ever try to do karate (if you tried to do the karate move, don't worry, visit the spaceport again and you will be given another one, but not from Katya). You will be given a mission for the Free Worlds. Just accept more and more missions for them. Those missions may be passenger transports, escorting ships, or bounties if you have a high enough combat rating. Note that you're not yet part of the Free Worlds. Only when you helped them enough and when you found the source of the terrorist attack you will be invited to join the Free Worlds. I advise you to buy a strong warship first before joining, otherwise you will have trouble with the combat missions (especially the "Liberate Kornephoros" mission). I used an Osprey with atomic engines before joining.