If you make a long click on the button «Pages» in the toolbar, a menu opens that lets you choose if you want to add a new following page, duplicate the current page or import a page or a set of pages from a file on your computer. This files has at least one page of image format (png, jpg, gif, …) or .pdf.
NB : for the title page (page 0), only 2 options are available (new page and import a page).