You can easily add our tacking script using the Script Manager in the BigCommerce site portal.
1. In the BigCommerce site portal, navigate to the Storefront, then select Script Manager, and click Create a script.
2. On the Create Script page, enter the information as in the screenshot below and click Save:
Name of script: CartStack
Description: Cart Abandonment
Location on page: Head
Select pages where script will be added: All pages
Script type: Script
Script contents: This will be your unique tracking code found here on your dashboard.
Additional information on the script manager in BigCommerce can be found here.