Anticipating that the answer would be to email Support, I've just done this but if I find out I could have done it myself, I'll post the info. here in case anyone else has the same problem.
With the way the system is right now, the only way you can fix a problem like that is to delete the submission and upload it again. Not the best solution, but that's the only thing you can do for now. If the mistake is minor (such as the word count is off by ten words), don't worry about it.