Hello,
To change Microsoft account's email address on your system, follow these steps:
- Open Start > Settings > Accounts > Your info
- Click the link Sign in with a Local Account instead
- Enter your information
Sign in then do this:
- Open Start > Settings > Accounts > Your info
- Click the link Sign in with a Microsoft Account instead
- Enter your information
Your email address is changed now.
Check the illustration of above steps in this video:
https://www.youtube.com/watch?v=32Dc4aRUkWk
Hope this helps!