Sub pages are connected to another page called the parent page.
These are used to display several sections of your current theme.
First, you need to create a new page following this tutorial.
To create a sub page, while in the page editor as shown at the above link, look on the right hand side where it says Page Attributes – Parent.
Click on the drop down menu labeled (no parent) and you’ll be able to choose a new parent page to link your sub page to.
Finish creating your page content as usual, and click the blue publish or update button to save your changes.
This is how sub pages are displayed within the dashboard under pages – all pages, with a dash (–) before their names. In the example below, the About page is the parent page to the next four sub pages below it.