The Password Self-Service Facility allows you to change your own password at any time. Just verify your identify by logging in with the correct username and password or, if you have forgotten your password, by correctly answering security questions.
To use the system when you have forgotten your password you will obviously need to have set up your security answers previously. This is done simply by logging in and clicking 'Set up Responses', and it is advisable to do this the first time you use the system. If you have not set up your responses to security questions and you subsequently forget your password, then you will not be able to use the self-service facility.