For abandoned cart, here comes a logic that user will have done "Add to Cart" but NO "Purchase" would have been done.
That means go into admin >> property tab >> Audience Definitions >> audience then click on "+New Audience"
Select "Create New" in the "Audience Definition"
Then select "Enhanced Ecommerce" from the left tab and select "Revenue per user = 0"
Go into "Conditions" in the left tab, select your "Add to Cart" goal, which you must have made, make it to "per user > 0"
Your audience will be made according to it. Click "Apply" & publish wherever you want.
Keep in mind it takes around 24 hours for the audience data to come into analytics and get published to any other tool.