Changing width and height is not possible by direclty edit css for CK Editor. You need to set with it's configuration javascript.
If you are using Snow theme than on line #30 find below function
function head_script() // change style of WYSIWYG editor to match theme better
{
qa_html_theme_base::head_script();
$this->output(
'<SCRIPT TYPE="text/javascript"><!--',
'if (qa_wysiwyg_editor_config)',
'qa_wysiwyg_editor_config.skin="kama";',
'//--></SCRIPT>'
);
}
now replace with below and set height and width whatever you want.
Note: if you dont want to set width than you can remove that line
function head_script() // change style of WYSIWYG editor to match theme better
{
qa_html_theme_base::head_script();
$this->output(
'<SCRIPT TYPE="text/javascript"><!--',
'if (qa_wysiwyg_editor_config)',
'qa_wysiwyg_editor_config.skin="kama";',
'qa_wysiwyg_editor_config.height=100', // chang to your height
'qa_wysiwyg_editor_config.width=400', // change to your width
'//--></SCRIPT>'
);
}
If you are not using Snow theme than add this entire function in your theme file.