Open your preferred text editor. We have an under-development Chrome apps plugin for Sublime.
Make sure you are using Chrome Canary. Access chrome://version and check if there is a canary keyword at the end of the first line:

Enable flags in chrome://flags
Enable Developer mode in chrome://extensions:

Note: Open the chrome://extensions page in its own window and keep it assessible as you work through the lab.
You will use this page quite a bit to load and reload the Todo app.
If you don't have it yet, install git and run:
git clone git://github.com/GoogleChrome/chrome-app-codelab.git
In 2 - Create Basic App, you will create your first Chrome packaged app!