Log into your account and go to your dashboard. In the menu on the left-hand side, click "Manage Gallery". Then click "Manage Content" in the button bar in the center of the screen. From there, click the pencil-and-paper icon under the thumbnail for the content you wish to edit. Alternatively, when on a submission page, click "Submission Tools & Stats" beneath its description, then click the yellow "Edit" button on the drop-down screen.