If you're looking to add the bizible script in Google Tag Manager, please make sure to prioritize the bizible script in your firing order. Please use this support article by Google to learn more.
1) Once you've opened up GTM, add the bizible script on your website container. Make sure to select Custom HTML tag.
2) Use the bizible script below and incorporate it in your container.
3) Click the button to
+Add a Firing Rule, so that you can tell Google to load our snippet on :
4) You should have something similar to this:
5) When you are ready, go to the Container Draft Overview section on the left. Click the button to create a new version of your container and publish the changes.