New Content can be added either through the on-page editing UI or the Site Admin UI, it depends only upon what you are comfortable with. All new content on your audience-based navigation (undergrad, grad, prospective, etc.) needs to be added underneath the correct navigational menus using either interface.
The addition of the majority of new content in AEM begins with “Creating a Child Page,” within a given section of the site. Once a child page is created, and a template selected (don’t worry, its way easier than Open Text), then you either “build” the page by adding components (dragging and dropping from Sidekick), or fill in the fields already programmed for the template (News and People). To access these fields, select the Page Tab from the Sidekick, and then select Page Properties (this is also how you edit existing content). You may also add additional content to predefined templates like News and People by dragging and dropping a component into the “Drop Zone” at the bottom of the page.