A content management system is software that allows you to create and manage webpages easily by separating the creation of your content from the mechanics required to present it on the web.
In this site, the content is stored in a database. The look and feel are created by a template. Joomla! brings together the template and your content to create web pages.
To login to your site use the user name and password that were created as part of the installation process. Once logged-in you will be able to create and edit articles and modify some settings.
Creating an article
Once you are logged-in, a new menu will be visible. To create a new article, click on the "Submit Article" link on that menu.
The new article interface gives you a lot of options, but all you need to do is add a title and put something in the content area. To make it easy to find, set the state to published.