HABMC is a massive codebase. If it were a person, it would probably be a guy named Larry with a penchant for vacuuming up his roommate's binary-O's. Dammit Larry.
Provided here are three mostly-discrete tutorials: one about Ruby, the programming language, another about Rails, the framework, and the final one about HABMC itself. Let's start with the ruby one. JK, if you're using windows you have to go here first.
Or you can access them from here