To add a new edition of any type, whether it be AP, Variant, etc. Just make a post in the Error Correction thread: viewtopic.php?f=8&t=108718&start=9825
With a link to the listing of the main edition, and specify the details for the new edition you want created. E.g. Run size, dimensions, release date, price, etc.
If there's a difference in the image (like in the case of Variant editions), go ahead and upload the new image to the existing listing in advance by clicking on the Add Image link to the left of the listing detail page.