Approve this iPhone

Hello everyone,

I just updated my iPhone 6 and iPad Air to iOS 11. I'm told I need to "Approve this iPhone" and to obtain a verification code from another device. I can get the code, but there is no provision to enter it on the iPhone. What am I supposed to do with this code? I have the same problem with the iPad. I'm guessing this has to do with the new mandatory two-factor authorization, which I had not previously activated. Advice is welcome.

Thanks






I didn't find the right solution from the internet.
References:
https://arstechnica.com/civis/viewtopic.php?f=19&t=1402279

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