Sitefinity RadEditor Adding Custom Styles
Category: Telerik Controls and Sitefinity
The first thing you should do in your App_Themes/YourThemeName/ is have your styles seperated out into two files. One that would be included in the rad editor as well as your page and one that would be only for your site. The reason is that you don't want some weird body styles getting applied inside the rad editor.
Once you have that done, simply edit one of the following files:
/Sitefinity/Admin/ControlTemplates/EditorToolsFile.xml
This is the ToolsFile that is included in the radeditor ie. for Generic COntent editing. Now, you can add a css files node under the root node like this:
You can also modify this same file under the classes node and add in which styles should be available to the end user while editing in the RadEditor. There should already be an example in here.