We are currently in the process of creating a new editor. We are launching new products a few at a time, so in the meantime you'll find different editor experiences for different products. If you have any questions, please contact us.
Photo Book Editor:
To change a page layout in a photo book, navigate to the Layout tab on the left side of the editor, decide which layout you want, and drag and drop it to the preferred page.
For a video, see below.
Editor for Other Products:
To change the layout of a print, frame, etc, navigate to the Layout tab at the bottom of the editor, decide which layout you want, and click to add it to the preferred page.