Outseta Custom Code Addition

I’m trying to set up a banner using web flow where it will display however many days are left on the user’s free trial before it expires. The trial information has to be unique to each user and taken from their account, I know I can use data attributes to do so but am unsure on how to actually do it. The banner itself is pretty much done, the only issue is adding the custom code that I need to add and getting that to work.

Here is my site Read-Only: Webflow - Smart Course