...
To get started, expand the Content section (Tab) of your StoreFront and click on Upsells. If you do not see Upsells, then you are not running a theme that supports them.
Create a Path
The first thing that you want to do is create a path by clicking on the Add Upsell Path button. A path is a sequence of offers that a customer will experience during the checkout if they have an item in their cart that triggers the path. A customer will go through each path that they qualify for starting at the top of the page and working their way to the bottom.
...