Go to the Gift with Purchase section in the navigation sidebar:
Click New Gift with Purchase
Enter the Name of the Product - as you want it to be displayed in the chat
Put in the Shopify Product ID
Give it a short description - as you want it to be displayed in the chat
Enter the original price of your add-on in the Display Value Box - Synthetic value will be greyed out as you give it for free.
Upload an Image of the Product
You can see a preview of how the gift with purchase will appear to customers at the bottom of this page.
Click Save in the top right.
Then, go to the Rule Setup page for the Rule you want the gift with purchase to appear on:
Go to the Gift with Purchase tab
Select your gift with purchase from the dropdown menu
Click Add
Click Save in the top right
Your gift with purchase is now active when customers reject Nibble's final offer.