Change display name
You use your display name whenever you sign in to your account. You'll also see it on any Windows 10 devices that you've signed into with your Microsoft Account, and it's the name people see when you send emails or participate in an Outlook.com group. This name may differ from your local account's display name.
Here's how to change your display name if you're signed in to your Microsoft account:
Sign in to the Your info page on the Microsoft account website.
Under your name, select Edit name. If there’s no name listed yet, select Add name.
Enter the name you want, then type the CAPTCHA and select Save. Some names may not be allowed if they contain blocked words or phrases. If you get an error when you enter your name, try a nickname instead.
If the display name doesn't change right away, or if the old name is still showing in emails, your information may be cached. To get the name to update quickly, you can switch to your local account, then sign back in to your Microsoft account.
The display name doesn't change your gamertag. If you want a new gamertag, see How to change your Xbox gamertag.