Navigate to your Workspace in Google Tag Manager, select tags and add a new Custom HTML Tag. Now get the snippet from your Platform in the Hull Dashboard and paste it into the HTML field in GTM.
If you don't have a snippet already, get one by following this guide Getting Started with Hull.js
The code snippet of the platform looks like the following:
In order to make it work in GTM, we have to adhere to strict HTML standard, so we have to prefix platform-id and org-url with data-:
That's all for the snippet.
Make sure to check Support document.write before you move on to configure the Triggers.
The answer to what trigger really depends what you have configured in your GTM workspace. For starters you can stick to All Pages:
That's it, preview your page and check in your Hull organization that page views are captured appropriately.