In the Accessories tab you will be able to add in the accessories you are looking forward to buy / or sell. 

  1. Tap on "+ Add Item"
  2. On "Item" Field, enter a friendly name for you to recognize the item
  3. On "Regular Price" Field, enter the price on the tag
  4. On "Discount" Field, enter a discount percentage rate
  5. Tap "Done"

Keep following the same steps until you are done adding items.  You can use your current location or any other location for the Sales Tax.  You will need the Postal Code to get the Sales Tax Percentage.  

Sometimes, you will see a button that says "AIP" at the bottom.  If you see that button, it means that that item list with the prices entered may qualify for an Accessories Installment Plan on your AT&T Account.  When you tap "AIP", it will launch an alert view telling you how much you will pay upfron, and how much that list will be monthly on your bill.