Charge an item to a potential buyer via either the comment section of your post, or through a private message with a potential buyer.
Have the buyer scan the unique QR code associated with the item your selling. This can be found on the “Selling” tab by tapping “Show QR code” for the associated item
Your buyer can choose to either pay you via cash or Venmo. Once they decide, boom, your item is sold. Who doesn’t love more money?