Security info is an alternate email address or phone number that you add to your account. If you forget your password, or if someone else is trying to take over your account, we send a security code to that alternate email or phone number. When you give the code back to us, we know that you’re really you and we can get you back into your Microsoft account.
Here's how to update that security info:
1. Go to https://account.microsoft.com/account/ and sign into your Microsoft account
2. Select Security and then select Update my info
3. Sign into your account again and select Add security info
4. Choose to add a new phone number or email address, add your new info, and select Next
5. Enter the code sent to your new phone number or email address and select Next
How to create a Microsoft account
Learn more about Microsoft account security info & verification codes