With Google Tag Manager, you are able to edit and update measurement codes and related code fragments. The tag management system allows you to configure and deploy tags on your site from a web-based interface. Tags help boost your sites SEO rating and overall ROI. The purpose of Google Tag manager is to help easily optimize the proper tags for your site, reduce configuration errors, modify, and deploy tags instantly.
From for Unified Admin, go to Partner Apps>Google Tag Manager. Add your Container ID into the indicated login. You can create a container ID when you create your google account or add an ID to an existing account.