This is useful for Google Tag Manager, remarketing tags, scripts, CSS and other code to your pages when you need it on every page and can't put the script or code in the body of the page. There are 2 locations, one that places code in the <HEAD> and another that places the block in the <BODY>.
1. Simply go to the website editor
2. Begin and go to edit a revision of your website.
3. Go to website Options.
4. Add your code to the Script block(s) and Save.
There are also page level HTML blocks on Page Options.
Remember, once you have made updates, you have to publish your changes to update the website.
NOTE:If you need to add script in a specific location on a page, look at the script control.