1 - Log in to your Wordpress website as an admin
2 - Go to "Plugins - Add New
3 - Search for "Head, Footer and Post Injections" and find the plug called "Head, Footer and Post Injections" by "Stefano Lissa":
4 - Install and Activate the plugin.
5 - Go to "Settings", then "Head and Footer" and paste the remarketing or call tracking code in the "<HEAD> PAGE SELECTION INJECTION" on EVERY PAGE as shown, then scroll to the bottom and click "Save".