Customize Category Title in Atahualpa theme

How to use this plug-in with Atahualpa ?

http://wordpress.org/extend/plugins/.../installation/
************************************************** **************
Under Appearacne -> Theme Editor in the WordPress admin, select "Header" from the list and replace <title><?php bloginfo('name'); wp_title(); ?></title> (or whatever you have in your <title> container) with <title><?php if (function_exists('cat_seo_title_tag')) { cat_seo_title_tag(); } else { if (is_category()) { single_cat_title(); wp_title(); } else { wp_title(); } } ?></title>
************************************************** **************