It's possible to watch private YouTube videos if the uploader sends you a viewing link. Private YouTube videos aren't shown in YouTube search results.
Press the Esc button to bring up the menu, and select the Settings option/cog wheel from the menu on the right. Next, click on the House icon, as shown in the image below: On the next screen that ...
To share a private YouTube video, you'll need to head to the YouTube Studio editor. There, you can send it to any email address.