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How do I make my theme support Real WYSIWYG

If your theme uses more than onw style sheet, then you should add a filter on real_wysiwyg_style_sheets and add the URI for you stylesheets to the array that is passed in. If you have stylesheets that are only for IE 6, then you can create a filter on real_wysiwyg_style_sheets_ie and add your IE 6 stylesheets to it's array. If you have inline styles that need to be applied, then create a filter on realwysiwygextra_css and add your required CSS to the string.

You will also need to update you stylesheets so that the CSS that applies to a post also applies to an element with a class of mceContentBody. If you don't have it already, Firebug for Firefox is excellent for determining what styles are applied on an element. You can use this to see what is applied to the post and create extra rules for the mceContentBody for anything it missed. Finally, I use screenshots of the post in the editor and as published to compare the styles and tweek the mceContentBody style as needed.