Forget Microsoft account password help
You can visit the Microsoft login page and follow the "can't access my account" link to reset your password.
If you want to change the Microsoft account you use on your phone completely, you'll need to reset your phone to its factory settings.
Microsoft also has a help site related to Microsoft Accounts and your Windows Phone which you can reference.
Hope that helps you. Good luck.
I forgot my Microsoft account password to update my Whatsapp