references - Open Trip Planner Tutorial

I was wondering if anyone had a good tutorial for Open Trip Planner. I am not an experienced programmer and I am having a lot of trouble understanding what the documentation wants me to do. I got through basic usage, but after that I became very confused. For example, I think the next relevant section is configuration. The first paragraph is about build directories. What exactly is a build directory? I've looked all over the internet for, but I didn't see any tutorials, and only a handful of stack overflow/exchange questions.