Customizing the TinyMCE Editor
Adding Style Choices to the Editor Dropdown
Create a custom stylesheet with the styles you want to use. Make it part of the template I'm using for the site. My top-level template css file is template.css. Add a line to this file:
@import url("article.css"); /* Styles used in editing articles available to the wysiwig editor */
Create the article.css with the styles you want to have in the editor.
Upload the edited template.css and article.css to the Joomla template directory.
Extensions > Plugin Manager
Editor - TinyMCE 2.0
In the box labelled "Custom CSS Classes", enter the path to the CSS file froim the site root. E.g.