My phone got stolen and I’m locked out of my iCloud how can I regain access

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If you forgot your Apple ID password - Apple Support

If you forgot your Apple ID - Apple Support

Recover your Apple ID when you can’t reset your password - Apple Support

Try going to iCloud.com/Find using a computer browser and then use the links MrHoffman posted. You need to use 'Find' to be able to log in without a verification code.

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.   

Yes, you can easily Sign into your iCloud by simply providing the Apple id and password in any apple or iTunes system