To create a sequence of emails and actions to recapture potential sales from abandoned carts, go to the Messaging & Workflows Tab -> Automations Tab
When you click on Create Automation you will be prompted if you want to create a Blank Automation or Abandoned Cart Automation. (This is just a template that will help save you some time)
You can see that the trigger of the Abandoned Cart is the abandonment of a cart/checkout that triggers the start of this flow.
The marking of an order/checkout as abandoned is set from your Store -> Settings -> General (Abandoned Cart Tracking)
Make sure to set a goal for your automation that ends the automation when the abandoned cart is recovered/purchase occurs so the customer doesn't receive any more emails from the flow.