Unless the manuscript guidelines provided by your publisher specify otherwise, it is not necessary to put it in "book-fold" view. Just submit it as a Word document with a normal full-page layout.
The reason you want to do this is because you don't know what trim size the pages of your book are going to be. After you submit your file, it will go through editorial staff and on to someone called a "compositor," who will arrange the text on the pages ("layout") based on the specifications ("trim size" or page size, margin width, font and font size, etc) of your book.
