To add a page go to hamburer menu ( ) and click on "Add a new page"[1] and select the type of page [2] you want.
In order to create a childpage(subpage) under a specific page, select the desired page [1] and click on "Add Child Page" [2].
To Remove a page or a childpage(subpage) select [1] the unwanted page, go to options and select "Delete Page" [2].