Some of this is basic, but most of it is quite relevant and useful
These videos cover the basics of high power rocketry as it related to hobbyists and college teams. Feel free to skip or fast-forward through the slow parts, but on the whole these are relevant and useful to what we do. The target audience is NASA Student Launch teams--a competition STAR has competed in!
https://www.nasa.gov/stem/studentlaunch/hp_rocketry_video_series
NASA has also nicely compiled all the information needed for L1- and L2-level HPR projects into a ~100-page written document! Check it out here if you're not a fan of watching videos, or if you want a more detailed guide to accompany the videos: https://www.nasa.gov/sites/default/files/atoms/files/sl_video_instruction_book.pdf