Once you've completed an Artwork Upload, you'll be taken to your Artwork Overview page. From here, you'll be able to see a high level view of all the information you provided during your Artwork Upload.
When looking at your Artwork Overview Page, clicking on "Edit" will bring you into the various sections to Edit any information you provided during Upload.
If you click "Edit" on the Images section, you'll be taken into the experience where you can now provide additional images to your Artwork Upload.