Change your account password anytime by following these steps:
Select Menu> Office 365
Select Settings> Change your password.
Enter your old password.
Create a new password and confirm it.
Select Submit to finish and change your password.
In case you have forgotten your password and are unable to access your account, click on the Forgot my password link on the sign-in page and follow the instructions there.
If you are still unable to access your account after using the Forgot my password facility, try the Microsoft Online Password Reset facility.