The Notebook holds all of your Notes, Followed Highlights and My Highlights.
To add a Note you must first create a highlight. Tap and hold your finger on a word. Drag the end point to select all the text that you want to highlight. Then tap “Create Highlight” at the top of the screen.
To add the note simply tap on the highlighted text in the book and then in the menu that appears at the top of the page click the note icon (it is the paper with a pencil on it).
Type your note and click Save. This will take you back to the book.
If you have subscribed to another Bookshelf user's highlights (example a professor, coworker, or student) their highlights will show up in this section.
Any highlights you have made will also show up in this section. To go to that highlight simply tap on it and you will be taken to the specific page.