To create the sequence of emails and actions to all abandoned cart users you'd need to go to Email Marketing & Automations -> Automations where all your flows are created.
If you don't have an abandoned sequence yet, when you create a new automation you will be asked if you want to create a blank or Abandoned Cart flow. This is a template we've created to save you 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
You should also have a goal to your automation flow that leads the user outside of the automation when the abandoned cart is recovered/purchased so that no more emails are sent to the users in the flow.
Our personal recommendation is to use our pre-defined Abandoned Cart automation flow as it comes with 3 beautiful emails that you can fully customize to your liking.