Drupal does not have a built-in head-code box, so the simplest approach is a small free module that injects it site-wide.
Step 1: Copy your install code
In Converly, click Install in the left sidebar and copy the code shown at the top. It is unique to your site. See Install Converly for the full walkthrough.
Step 2: Add it to Drupal
Install and enable the free Asset Injector module. Add a new Code snippet containing your Converly code, set it to load site-wide in the page head, then save and clear the Drupal cache.
Check it works
Submit a test entry through a form on your site, then open the Activity page in Converly. If the code is installed correctly, the event shows up there within a moment.
Paste your own code
Any code shown in a screenshot is only an example. Always paste the exact code from your own Install page, which contains the key that is unique to your site.