How to create and edit articles in Joomla
To create or edit articles in Joomla log in to your site's backend (admin panel) and open the Article Manager (either from the button on the backend's home page, or from Content>Article Manager).
To create a new article click on the New button in the upper right corner of the Article Manager. On the Add New Article screen you can type the content using the built-in editor, and configure different options. The obligatory options that you have to set are the title and the category to which the article will belong (they are marked with an orange asterisk). When you have set everything click on Save & Close to return to the manager.
To edit an article just click on the name of an existing article in the Article Manager, or mark the checkbox in front of it and click on the Edit button in the upper right corner.
For some more information visit the tutorial on creating and editing Joomla articles.