These instructions assume that you're familiar with Linux and system administration.
You will need an internet connection to set up the kiosk, even if all the pages will be loaded from disk when it's running.
Note that a "closed" website is one with no links to other websites or to pages with no links back to the rest of the site. The idea here is to only allow users to access a limited set of pages since the kiosk is provided for a specific purpose. If you develop your own content for the kiosk to display, make sure that all pages have at least one link back to the rest of the site; the Back button isn't displayed by Chromium when in kiosk mode.