How do I add an email for two step verification

I don't think either two-step verification or the newer two-factor athentication (which do you use?) use email for verification purposes.

You may also wish to read the articles 'Two-factor authentication for Apple ID' ( Two-factor authentication for Apple ID - Apple Support ) and 'Get a verification code and sign in with two-factor authentication' ( Get a verification code and sign in with two-factor authentication - Apple Support ). Various sections contain information that is useful in understanding about the trusted devices (an iPhone, iPad, or Mac that Apple knows is yours) system, and how to get a verification code on a trusted device or at a telephone number.

In the end you may also need to resort to account recovery (mentioned in the article) if you cannot get a code.