[Plugin: Custom Widget Area] Where to write the code? Bar in every page.

Where exactly shall I put the code? I’d like to have a sidebar in the header of every page.
And the shall be like this?:

<?
if (!function_exists(‘dynamic_sidebar’) || !dynamic_sidebar(‘Header Widget Area’)) :

endif;
?>

Thank you.

http://wordpress.org/extend/plugins/custom-widget-area/