I have an older, Apple ID when I set up Cloud. I've tried to log in and use it as my Main Apple ID. It tells me that it's in use by another, which is me. How can I log in to this email to use for my primary Apple ID?

Here is my question in a bit more detail:

I have a **@me.com Apple ID when I first set up Cloud. Evidently I have **@cloud.com that I thought was an alias for the @me.com Account. I have been using an Apple ID (**@prodigy.net) from my very first Mac.

I've tried to log in to the **@me.com account and set it as my Main Apple ID. It tells me that it's in use by another, which has to be me.

How can I log in under this **@me.com email to use for my primary Apple ID?

MacBook Pro with Retina display, OS X El Capitan (10.11.1)

BTW, Sir Winston is my most admired leader of the past century and a half. He's the most underrated figure in history.

When BHO removed a bust given to the American people by the people of Great Britain, told me everything I needed to know.