Look in the top right corner of your page for the menu that says Unpublished (or Private or Published). Select Change Status & Share.
Every guide begins as this.
Change to this soon, so that you can share what you're working on with colleagues. Use the friendly URL. (Anyone with the link will see it, but since it's not yet linked anywhere, search engines won't find it yet).
Change this when you're ready for the page to go live.
It will then automatically appear on our pages that list all the guides, and it will eventually be indexed by Google. (Be sure to add the appropriate tag for your Subject or Topic Guides, or they won't show up automatically).
Preview your guide
Look in the top right of your page for the icon that looks like an eye. Click that to preview your page in a new tab.
Now is a good time to preview your guide to see how it will look. (The editing interface looks quite different from what the public will see).
Work with your preview frequently while editing your page. It's handy to keep it in a new tab and hit refresh to see your changes.