Implementing SiteGainer on your website is easy.
First, you need to find your script that you will paste into your <head> tag. It’s found below websites -> click your website -> Implementation script.
Then take the script from the textarea and add in the absolute top of your <head> tag on your website.
Do not implement SiteGainer with Google Tag Manager, this will make the script load after your website is loaded, making any changes you do with SiteGainer also appear after your website is loaded.