It's good practice to change your passwords periodically (or after someone else may know it) - so it's possible you may want to update your Windows 10 login password at some point. The following steps work to change your password for both local and Microsoft accounts.
To begin, click the start button and select Settings:
Now click Accounts:
Then click Sign-in Options from the side menu and click Change under the "Password" section:
You'll then be prompted to enter your current password and then enter your new password twice. The entry page differs slightly depending on if you are using a local or Microsoft account, but the process is the same either way.