Hello alambert83! You need to be able to prove that you're allied with any communist minor faction to join CI, but if you're looking for a particular minor faction in order to help CI's goals, you can pick any communist minor faction within a 60ly radius of Manite. There are some wars that need winning, if you're into combat. It's a fairly easy way to grind reputation and it always helps to win wars. (other sorts of help are welcome but sometimes it can interfere with long term projects, like trying to get a minor faction to expand from a specific system.)