I think they don't actually have any referral system or such... it's not really designed for earning tokens directly either, though the ingame resources, ships and especially planets are being traded for decent rates in the community.

It's a rather slow game and it'll take a few weeks of build-up before you'll be able to really "play" the game.

That being said, just head over to @nextcolony for more info or sign up with your steem keys on https://nextcolony.io