Google Tag Manager scripts can be added to your Landing Page. The option to add this information can be found both within the Builder as well as in the Dashboard.
NOTE - This is a page-level setting. i.e You can have one set of Google Tag Manager scripts for your landing pages and this cannot be changed for each of the Variants for that landing page.
In the builder - Navigate to Global Settings Panel > Tracking Codes and click on the Tracking Codes Tab. Add the Head and Body scripts in the respective provisions.
In the Dashboard - Navigate to the tab Settings > Tracking Codes > Other Scripts within the respective landing page. Add the Head and Body scripts in the respective provisions.
NOTE - Follow the link to knowHow to get your Google Tag Manager Script