The default text editor is alright for entering text, but some of the advanced capabilities (such as adding images or inserting hyperlinks) aren't really easy and intuitive. Let's install the Joomla Content Editor (JCE), a very popular and freely available replacement for Joomla's default editor (which is called TinyMCE). For many Joomla users, JCE is the first thing they add after installing Joomla.
Go to http://www.joomlacontenteditor.net and download the "single installation package" for the current version of Joomla. The installation package is a compressed file.
Navigate to Extensions | Extension Manager. Click on Browse to locate the compressed file you just downloaded and click on Upload & Install. Once both are installed, you'll see the message: Installing component was successful.
Tell Joomla that you want JCE to be the default editor. Navigate to System | Global Configuration. On the Site Settings panel, set Default Editor...