Accessing the control panel is done via logging in Joomla!'s back end. Upon log in, you are looking at the control panel. If you want to access the control panel from another area in the back end, simply go to Site > Control Panel.
The control panel provides access to many default Joomla! functions and features. It allows you to create a a new article. You can also manage existing articles, sections, and categories. Also available at the control panel is the media, menu, and language, and user managers. Finally, you can access your site's global configuration settings.
The icons available to you in control panel are:
Add New Article
This will take you to a new article creation page where you can create new content, and then select a section and category, and then save the article. Its useful for quick and easy additions to your site's content.
This will take you directly to the Article Manager where you can manage all of your current articles.
Front Page Manager
Similar to the Article Manager, this icon will take you to the Front Page Manager so that you can manage all of the articles published to the front page.
The Section Manager icon directs you to the Section Manager. You can create new sections, and publish/unpublish current ones.
As you might guess, this takes you to the Category Manager. You can create new categories, and publish/unpublish current ones. You can also change which section each category is published in.
The Media Manager will allow you to manage files on your web server. You can delete existing files or upload different ones from your hard drive. You can also create new directories on your web server's file system.
The Menu Manager icon takes you to the Menu Manager. Here you can manage the current menus by creating new ones, deleting current ones, or directly managing each menu's subsequent menu items.
Following suit with all of the other 'managers' in the control panel, the Language Manager allows you to manage installed languages by setting one to be the site's default language.
The user manager does just what you might guess by it's title. It manages users. You can create new users, delete existing ones, change passwords, change language and time settings, and even change which WYSIWYG editor the user has access too. Lastly, but perhaps most importantly, you can assign the user's user group, giving the user access to different access levels and different abilities in your site.