Go to: https://appleid.apple.com/signin

Login:

Under “Apple ID and Primary Email Address” click “Edit”
 

Enter the email address you want to use and click save.

Note: If you’re trying to use your current email on a new Apple ID, use something else here for your email and then create a new Apple ID account using your preferred email address. (If you need an email address you can get one for free here.)

Note 2: Remember to update the login info on your computers.
 

To create a new Apple ID using your old email, Go here https://appleid.apple.com/ and click “Create an Apple ID” and enter your old email as the Apple ID Email.