New users to Joomla have a number of basic things that they want to do. Getting used to these few items will give you the confidence to try other features. You should certainly be able to maintain most of an existing Joomla web site if you know these basic features.
• Admin Panel Menu
• Create a new article.
• Edit an existing article.
• Add a photo/image to an article.
• Adding a menu.
• Creating a module.

Admin Panel Tutorial