When uploading, you can decide whether you want the photos to appear full page or two per page. However, there is also a way to put 3 photos per page.
First, click 
in the upper, left-hand corner and you will find yourself on the editing page.
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 dragging photos from one page to another, while having an overview of the whole book. You can also control the size of your pictures:
Click on each picture individually: 
stands for full size (1 photo per page), 
for double size (2 photos per page) and 
for 1/4 size (4 photos per page). The best way to put 3 pictures per page is to put one with portrait orientation (vertical) and two smaller pictures next to it. In order to do it, press a double size for the picture with portrait orientation, and 1/4 size for the smaller pictures.
However, one of the pictures doesn’t necessarily have to be with portrait orientation. Set 1/4 size for 3 pictures that you want to appear on the same page, and set full page or double-size format for the photos that appear before and after those pictures. Done! Enjoy your 3 landscape-oriented pictures on one page!
The “Mix it!” button randomly assigns sizes for your photos, try it to see how your pictures can appear in the book!
Don't forget to click the 
button, otherwise your changes will be discarded.
