To add a book ribbon to the text, click on the book ribbon icon in the upper right corner of the main window.
To access your book ribbons later, open the lower option bar by swiping up from the bottom, clicking the brown bar on the bottom of the screen, or pressing Win+Z.
Select 'Study' and then 'My Stuff'.
In the My Stuff folder, you will see your most recent annotations listed. You can select the book ribbon if it is listed here, or you can find it by selecting 'Ribbons'.
Here you can find all your book ribbons and sort them into categories.
To create a new category, select 'Add' and then 'Category' from the lower menu bar. Give the category a name and click in the My Stuff list. You should see the category appear in the list.
Drag and drop book ribbons into the appropriate category.