Divi Integration Tab allows you to add some custom changes to your site. It allows to add changes in HTML format. This means you can add a script, plain text, html etc. PHP code is not allowed.
You can add your changes in four different fields based on where you want the code to be executed exactly:
In the <head> element;
In the <body> element;
In the top of your post pages;
At the bottom of your post pages;
You can find the Integration tab under the WP Admin > Divi > Theme Options > Integration tab:
