Open a terminal and cd to the directory you unarchived:
cd <the directory you just unarchived>
Within it you'll find:
koans: this directory contains the application and its lessons, it is all that is needed to advance through the koans themselves and it can be distributed independently
koans-lib: the directory for source code for the engine that executes the koans
koans-tests: the directory for tests to check the sanity of the application
Change directory to the koans directory: cd koans
If you are using windows enter: run.bat or sh run.sh if you are using Mac or Linux.
Developing a Koan:
Follow any of the existing koans as an example to create a new class with koan methods (indicated by the @Koan annotation, they're public and specify no arguments)
Define the order the koan suite (if it's new) will run in the koans/config/PathToEnlightenment.xml file
Optionally you may use dynamic content in your lesson, examples are located in the XmlVariableInjector class (and Test) and the AboutKoans.java file
About
A framework and corresponding koans to learn the core Java language, best practices, and TDD