Joomla comes with a built-in text editor: TinyMCE.
Although this is OK for many users, the need to change it to something more advanced may arise. When installed, you need to make sure that the editor is selected as the default editor.
I'll show you how to do that.
This is a problem that may arise oif you upload images to your image folder. The default configuration of Joomla sets the path to the image folder to images/stories. If you upload your images outside the stories folder you won't be able to access them from the editor.