In the App Editor, go to the Pages & Forms tab and use the βNew icon to add a new page to your App.
Zingy App Editor - New Page button
Select Page as the type and provide a unique ID for your page.
Please note that the ID of your page cannot be changed, but you can change the display name for the page.
The ID is used internally to refer to the page. The ID also gets used as the default name in the page's URL when you publish the page. You are allowed to change the name in the page's URL. See Page Publishing for more information.
Once the App editor creates your page, it will be shown amongst the list of pages.