We covered how to update the visibility of your books in another help article, but this article's goal is to show you how to change the visibility at the more granular highlight level within a book.
From the main Bookshelf view you can click on the Highlights option in the left navigation to see all the highlights and notes you've made in any book you have in your BookFusion account.
From the Highlights page you'll see all your highlights and the notes you've added to them. If you click on the three dots to the right of any highlight, you can choose the Privacy option to change the visibility of only that highlight you made.
Use the dropdown to choose who you'd like to be able to see this highlight. If the book it's in is visible to your friends but you want this highlight to stay private just set it to "only me" and nobody else will see it. If the book is only visible to you but you'd like to share a specific part of the text, you can change the highlight to "friends" and anyone you've added as a friend will see it on the Branch screen.
You can confirm the highlight's visibility from the Branch page. Next to the timestamp you'll see a small icon which will tell you what the highlight's visibility is. In the screenshot below it is a person because it's visible to friends but it can also display a padlock to show it's private and only visible to you.