Confirming your email address is an easy four step process. For more details on how email confirmation works, or to troubleshoot issues confirming your email address, please check out this article: Confirming Your Email Address
Step One: Visit your account settings and find the “Email” section. Simply retype the desired email address into the field where the email currently linked to the account displays:
Be sure to click the 'Save' button at the bottom of the page to update your email address.
Step Two: After clicking Save, a popup box will appear asking you to confirm your password. Click on the 'Save changes' button when you are finished.
Step Three: You will be redirected to your settings page, which will reflect an ongoing confirmation process (see the text highlighted in yellow, as shown below.) From here you can cancel this process if you change your mind, or re-send the confirmation email to yourself if you did not receive it.
Step Four: You’ll receive two emails: one to your old email address (if you have access to it) and one to your new email address with the confirmation link. Once you’ve clicked on the confirmation link the new email address is confirmed to your Twitter account, and you're good to go!