Where do I enter my Apple ID verification Code?

You will be promted when you sign in.

To see how to 'Get a verification code and sign in with two-factor authentication', click here --> https://support.apple.com/HT204974

- Use a Trusted Device: Mac, iPhone, iPad, Watch. Code is either generated automatically or manually using Settings on the Trusted Device.

- Text or phone call to a trusted telephone number (any telephone; even landlines).

- Get a code from an Account Recovery Contact --> https://support.apple.com/HT212513

- Instructions at the end about what to do if you cannot get a code and need to use account recovery.

My iPhone 11 Pro was and remains signed in to my Apple ID account. However, my MacBook Pro recently stopped accepting the same valid password, causing endless hassles. If I had to change the password, I'd have to take many hours to change it in ~20 places on >6 devices in several locations. My iPhone generates a Verification Code for that Apple ID account; is there some way I can use it to fix the log-in problem on my laptop?

Post that question in a new topic in the iPhone hardware forum. This forum is for questions about Apple ID.