Following is the article to change the Administrator User Password of Windows 2016 Server.
- Log on to the computer using the Administrator user and click on the Window button left the bottom corner.

- Select the Administrative tools and click on Computer Management.

- Click on Local Users and Groups >> Users

- Right Click on Administrator User and click on the set password button.

- Enter the New Password and Confirm Password and hit OK Button.

Now, you can log in to your VPS with the new Password.