Change (set?) phone number

Hello,

I want to add my phone number to my account.  I go to edit profile / contact info / phone number / add and try to add my phone number.  I can type in my phone number, but the green "change" button is kind of greyed out.

Is this because my account was created with Facebook?  Or am I doing something else wrong?

Is this on one of the apps?

They don't ask for phone numbers on the website. I wasn't aware that they asked it on the apps either.

This is on the web page (computer).

https://support.chess.com/en/articles/8584217-how-do-i-create-a-chess-com-account

Some people sign up these days using a phone number. You evidently signed up with your email address.

You don't need to add a phone number.

Oh, okay, thanks. That was very helpful.

Can you share phone numbers with other people if you know them?