Alrz, I'll just make sure you get a chance to ask questions, and are still reading it, feel free to ask when you want ^^
Skipping over the less important exact details of how they continued to colonize, it may have took a few years, but large sustainable human settlements were established across multiple planets, many planets had their own alien flora and fauna, the humans installed gigantic heat generating facilities connected to the core of the planets that would make the atmosphere warm enough to be comfortable, and a few planet also had the luxury of an artificial light source manufactured to orbit the planets and mimic a day and night cycle, but for most it was perpetually night.