Under My tickets > Listings in your StubHub account, click Upload PDF > Upload tickets. Find the file on your computer and click Next.
Proceed through the steps, selecting the Yes, this page is radial button and selecting the corresponding seat number in the dropdown. Choose No, a buyer should not get this page if not using that page of the file.
Click Continue when you’re done. If your listing doesn’t include seat numbers, you’ll only see “Seat GA” in the dropdown.