Open Settings
Click Accounts
Click Your info
Select Manage my Microsoft account if using a Microsoft account
Sign in to your account
Open Your info on the Microsoft account page
Click Edit name
Enter the new name
Enter the CAPTCHA
Click Save
Restart your PC
For a local account, open Control Panel
Click User Accounts
Click User Accounts again
Click Change your account name
Type the new account name
Click Change Name
For another local account, open Settings
Click Accounts
Click Family & other users
Select the account
Click Change account type if needed
Use Control Panel to rename the account if required
To rename the user folder, create a new account with the desired name
Move your files to the new account
Delete the old account if needed