To reset your password via Outlook OWA, you must firstregister for self-service password reset.
When registering for the self-service password reset, you must have two security methods in place so as to be able to reset your password; the recommended reset methods are personal e-mail account, cell phone, or security questions
Once you have registered your password reset methods, you may now proceed to reset your password online. For further reference, please see Microsoft's Password Reset guide.
If you do not need to reset your password but would like to change it before it expires: