In order to unlock all of the the editable pages in the book, click on the 'Advance Edit' button at the bottom left of the book builder.
You will be able to add photos to any pages marked with the 'Add Photo' icon.
You will be able to upload 1 photo to the Museum page, 1 to the Newspaper page and 3 to the Scrapbook page.
You can now also swap in extra photo pages into the book on any page that has an edit button.
The Wise(ish) Word range allows you to upload 3 photos at the beginning of the book.