The Navigation module will display an outline of links to any sub-pages (and sub-sub-pages) of the page you're working on.

Click on the Navigation Module

Heading/title is optional. There are no further steps to adding this module.

Click the top bar or use the ... (Power Dots) to change to Display mode for a clearer idea of what your page will look like. For an even better look at your page, choose one of the preview buttons in Tools on the right side of your screen.