Packaged apps are still evolving. We're giving you an early look at how to build them, but it's a developer preview; they aren't ready yet for building production applications.
This means that you can't just yet publish your packaged apps in the Chrome Web Store — but you will be able to do so very soon.
What you can do (as described throughout this guide), is load your unpackaged app to the apps and extensions management page and try out your app from a new tab in the Chrome browser.
In case you haven't tried it yet, here's how to load your app: