I Think i misunderstood your question.
if you edit the HTML Editor preset, and go to the styles page, you can select a style sheet to attach you can also select a class to be applied to the HTML Editor body.
when you make changes to HTML Editor, make sure you clear the browsers cache, CKEditor is largely javascript driven, once complied, the browser caches it, so changes will not be sean unless the cache is cleared and the browser is forced to recompile.