Beginners/Learn to use Joomla
From Joomla! Documentation
Portal:BeginnersRevision as of 20:32, 31 August 2012 by Tom Hutchison
Now that you have a working Joomla! site, you will want to start filling it with your own content and making it look just the way you want. Before doing that, it is a good idea to learn more about how to work with Joomla!. There are a number of very useful resources to help you with this.
One way is to learn by working with the sample data.
For support as you are learning, you can ask questions in the forums.
The Joomla! Demo site is a good place to try out many of these features if you have not yet done an installation.