Navigate to PAGES > ADD NEW , give the page a title and publish it. Incase of an existing page, just edit it in the backend.
Build the page using the Tatsu and Assign a unique ID to each section in its Settings Panel.
Enable Single Page Version in the Page’s Meta box settings.
To create the menu and add the Section Targets, navigate to APPEARANCES > MENUS, you need to assign the links in the format http://www.yourwebsite.com/#SECTION_ID . These links will then smooth scroll to its respective section.