Hello,
Thank you for posting in Microsoft Community forum.
Based on the description, I understand your question is related to add phone number to Microsoft account.
- Sign in to Manage how you sign in to Microsoft.
- Select Add emailor Add phone number.
- Follow the instructions to add a new email address or phone number to your Microsoft account aliases.
Reference:
How to add an email address or phone number to your Microsoft account - Microsoft Support
Have a nice day.
Best Regards,
Molly