To create a new Part, open the Project Navigator, select a Book, and do any of the following:
Open the File Menu > click New > choose Part (or press the ⌥⌘P key combination).
Click the plus icon (➕) beside the Filter at the bottom of the Project Navigator and choose New Part.
Book Summary Page
When a Book is selected in Project Navigator, a Book Summary Page bearing the Book’s title will be displayed.
Click the New Part link beside the space reserved for the Book’s cover image.