Click the 
button in the upper, left-hand corner and you will find yourself on the editing page. Then click the 
button in the editing menu.This is where you can find the storyboard of your book. Here, you can easily organize your story by changing the order of the photos. Just click the 
button and pick an option:
1. Rearrange chronologically. Click this button, and the photos will appear in date order, according to the date they were added (the date that is indicated on each photo).
2. Reverse order. The button pretty much speaks for itself: click it and all the photos will appear in the reversed order (as opposed to the chronological order).
3. Rearrange manually. Drag each photo in the book to the place you choose for it. In this case, you easily create your story putting the pictures in the preferred order.