ckeditor text formatting from CSS

hi there,
i have the editor setup in my site and is interacting perfectly.

is there a way to apply my site's CSS file to the editing window? this would mean that when typing into the editor, the text that would appear would be formatted as per my site's CSS and the heading 1,2,3,... etc would pick up the CSS

i hope i have made myself clear!

thanks for the help!