Sub-pages show up as drop down menu options on your site, like so:
Creating Sub-pages is an easy process. You can create a Sub-page from an existing page or when creating a new page.
If you are making an existing page a Sub-page, click on Properties under the page title in Manage Pages, then choose a page from the 'sub-page of' drop down menu.
If you're adding a new page as a Sub-page, you can select the Add as Sub-page Of drop-down menu and choose a page.