Since documentation exists the README file will not cover anything in depth. Also, note that since this is a learning project for most of the contributors, the documentation shall generally be kept as detailed as possible.
Skyl-OS is intended to be an experimental operating system. Its main purpose is for a bunch of geeky and interested university students to learn how OS development works. They say explaining something is the best way to understand how well you know it anyway; so what's a better way to learn something than to explain it to a C compiler?
Run make clean to clear previous builds.
Run make to build.
Run make run to...well, run.
There is a dedicated section in docs for this. Please read that if you want to start contributing.