In this example we are going to have some custom code, which we would like to be applied to our GlobalPatron form.
Firstly, go to https://tagmanager.google.com/ and login with a Google account (it's free to sign up)
After you have logged into GTM, create a new "Container" to store your custom code, and make sure to specify that this is intended for "Web" like in the screenshot below:
We now also can specify the trigger for this code to be loaded. In our case we want to use the trigger called "All Pages - Page View" like in the screenshot below:
We can now "Submit" and then "Publish" our snippet of code. (After you click "Submit" this will make the "Publish" button appear). At this stage you also have your unique GTM code (example highlighted in yellow below). This GTM code is needed for the final step which is when you are associating GTM with your form.
In the GlobalPatron platform, when editing a form, on the right menu click on the "General Settings" menu option near the bottom of the page to open a popup with these settings below, and enter your GTM code:
Your form now has your custom code from GTM running within it.
Note: to see your custom code in action you need to be viewing a published version of the form as the code will intentionally not render within the editor view of the form for security reasons.