Creating a Collection Filter for Shopify Products

I’m using the Scenario Template “Create a Post about a new product in Shopify”. It does a great job for pulling random products, but I want to filter it to only look for products in a specific Shopify Collection. Can anyone provide steps on how to add this filter to the scenario?

The current Shopify settings are Watch Product, Active, Published, Limit 1. Then it sends to Facebook for posting.

It sounds like it should be a simple step being added, and it’s probably right in front of me and I’m just not seeing it. Any help would be greatly appreciated!