I'm afraid that once the league has archived, it is not possible to change the email setting you had for the league. If you chose to have your email address hidden, your current commissioner will be unable to designate you as a commissioner for this league at this time.
You will need to wait until the fall, when the commissioner renews the league. You can set your email address to be visible to league members, and you then can be assigned commissioner powers at that time.
I know this isn't the answer you wanted to hear. If you have any other follow-up questions on this topic, please be sure to reply to this thread.