In June 2012, I purchased extra storage for my iCloud acct. Accidentally, I bought it for my email address for iTunes, thinking it was my ICloud acct. How do I move the storage I don't need for that email/username to my correct iCloud username/email acct?

If you bought extra storage for icloud, then the Apple ID that was currently used to connect to icloud is the account that got the extra storage. You seem to imply that you have another Apple ID that also is used to connect to (another) icloud account. If that's true, you can't move the extra storage from one account to another and you can't get your money back, since there's only a 15 day (or so) time period to get a refund.

You can only buy more storage for the other icloud account at this point.