How to Begin Adding Content to a Joomla Site
In order to create Menu Items (pages) for your site you will first need to create categories, articles and menus.

1. First, determine the categories your content will fit into. You will be able to add additional categories later if needed.
   To add a new category: Content Menu > Category Manager > Add New Category.
2. Secondly you will need to start writing articles for your site.
   To add a new article: Content Menu > Article Manager - Add New Article.
3. Lastly, you will create menus for your site. You can add menu items to the existing menu or add a new menu. 
   To add a new menu: Menus Menu > Menu Manger - Add New Menu.
4. To create menu items (pages) follow the instructions in this article: How to Create a Menu Item in Joomla.