Using Wysiwyg with p2theme

Actually i'm using p2theme. I want to replace a form in frontend by a wysiwyg form like in backend. I've try to use wp_editor but there is a big blank! If someone know how to resolve it.

my code :

 wp_editor('', 'posttext', array(
            'teeny' => true,
            'media_buttons' => false,
            'editor_class' => "marginme",
        ));