you cant use HTML Editor to edit the instance that is used in Power CMS.
to add styles to Power CMS, you need to edit the webassist/ckediedit/style_lists/stylelist1.js file
to change the toolbar, you need to open the content area and change either the admin toolbar or live edit toolbar selection.
to change the toolbar items that are available for each toolbar group, you would need to edit the database table that controls them. see this post for details: