How do I set up a third-party tag?

Third-party tags are set up within the 'JavaScript / Third-Party Tags’ section of the rule. To add a tag / script, first, expand the ‘Javascript/Third Party Tags’ section and click ‘Add New Script’. Then, in the text box, add a name and select the script type (Non-Sequential JavaScript, Non-Sequential HTML, Sequential JavaScript). Paste or type in the desired content into the text area and click ‘Save Code’. 

For more information on load order / script type, see help link here -https://marketing.adobe.com/resources/help/en_US/dtm/load_order.html