Private notes (notes not available to other users) can be shared now in two ways:
1) With your contacts
You can share note with specific registered users (Share with your contacts option).
2) Using link sharing
To enable link sharing, first switch toggle in Access tab to Link sharing on (visible only when Private only is selected).
Now, after publishing article, on the Links 
section you can find Private link that can be easily shared with other people. They don't need to be registered. Only you or the ones who have the link can read the article.
We would like also to remind that Premium users can create password protected notes, where note content and images are encrypted using strong AES-256 GCM algorithm.