Do you mean your video is set to private even though it is supposed to be public? If so, go to channel content and go to the video that is private. Click the eye and then select public, not forgetting to press publish afterwards.
( mine is greyed out because mine is already published as a public video.)
If you mean it is public but it is receiving so little views that it seems like it's private, then try changing up the title, tags, description, and thumbnail so that it is more searchable in YouTube search.
Make sure your description is written in full sentences, and a tip I always have followed is I have always tried to include the keywords from the title in the first two lines of my description (in sentence form) because when you see a video on the YouTube search page, the first 2 lines of the description is what you see.
Make sure the thumbnail is readable (if there is text) and not too much going on, while still making it interesting so that it is clickable.
Then when you do tags, you can use words from your description as some of your tags for starters. Hope this helps!