WP Hooks is a plugin for WordPress that allows you to add JavaScript, HTML, or other code to your
header and footer without modifying your theme. WP Hooks uses the wp_head() and wp_footer() hooks
built in to WordPress to add content to your header and/or footer. It’s great for those who have
custom JavaScript, CSS, or other code (Google Analytics, meta tags, etc.) in their header or footer
and don’t want to or can’t modify their theme.

Find more instructions and discussion on the WP Hooks home page.