You can add in extra content to the <head></head> section of your pages.
Login to your website.
Find the page you want to edit in your sitemap.
Click on the page, from the contextual menu choose "properties"
Then select "custom attributes"
Then select "Header Extra Content"
Place your content in the box provided, and save.
Clear the cache if you need to: Gray Line Licensees Clear Cache
If you'd like the extra header content to go on all pages, not individual pages, please see this article: