Follow these instructions to set up Gumstack using Google Tag Manager.
Launch Google Tag Manager and log into your workspace.
Click on the "Search Gallery" Button in the Tag Templates section
Search for "Gumstack" and click on the Gumstack Tag Template.
Click "Add to Workspace" button
You will be presented with a confirmation dialog. Click on "Add" to add the tag to your workspace.
Gumstack is now available as a tag in your workspace. You will now be able to use Gumstack in your current workspace.
Go to Tags in the menu, and click New
Choose Gumstack from the list