1. Create a navigation menu called
Cart upsell.
The handle needs to be:
cart-upsell
2.
[Trigger product]
Add a menu item and name it following this structure: "products/product-handle". This product will serve as the upsell trigger (the upsold product will be displayed IF this product is in cart).
3.
[Upsold Product]
Select the product to be displayed as the upsell for the trigger product defined in step 2 above.
4. Enable the upsell in Online Store > Theme >
Customize
> Cart > Sections tab > Scroll down to the Cart Upsell section.