I put together this little screencast that will walk you through getting started with the Koans project. If you haven't read my introductory post yet, read about it here. As you'll see its extremely easy, and its pretty fun too, especially if this is your first journey into unit testing.
As always, if after watching this and working on the Koans you have some good ideas for some additional tests to add to the project please send me a pull request on GitHub. If you are really limited on time and just want to share your idea you can always go to the README.md page, click on the "Edit" link, and add your ideas to the "Suggested Topics" section.