I find the easiest way to add your style sheet is to edit the custom files in the HTML Editor folder:
Open the HTML Editor folder and open the custom folder then the
contents_insert_ContentValueStyles1.xml and change it to suit i.e.
<?xml version="1.0" encoding="utf-8" ?>
<Styles>
<Style name="MyStyle-One" element="span" >
<Attribute name="class" value="MyStyle-One" />
</Style>
<Style name="MyStyle-Two" element="span" >
<Attribute name="class" value="MyStyle-Two" />
</Style>
<Style name="MyStyle-Three" element="span" >
<Attribute name="class" value="MyStyle-Three" />
</Style>
</Styles>
etc etc untill all the styles you require are entered. Then copy this and past it into the
contents_update_ContentValueStyles1.xml file ok thats the first bit second open the content_insert_ContentValue1.js file and look down at the bottom and change this line to your css file (making sure it is relative)
FCKConfig.EditorAreaCSS = '../../css/mystylesheet.css'; // relative to fckeditor/editor/fckeditor.html
Do the same for the contents_update_ContentValue1.js file
and that's it refresh everything log out back in clear your cache etc it always works for me and even though I have HTML Editor 3 you don't need it to do this hope it helps Alistair