From the book preview, click "edit pages" and navigate to the page that says "sort pages" at the top. Select the image you would like to edit then click "edit label" from the options. You can select a new name, age, or tag and add a date or caption to the image. When you are done, click the "x" in the top right corner twice. Your changes will save automatically. You can edit multiple images at once by selecting the desired images and then clicking the "edit" button at the top right of the screen in the blue bar.