If you are logged into MyCadet you can update your password by clicking on your username in the top right corner and selecting Change Password.
If you are not logged into MyCadet, you can reset your password from the MyCadet sign in page, by clicking Forgot Password:
If you have done this and the password email has not arrived after a short while, add no-reply@cadetdigitalservices.com to your safe senders list/ email contacts before re-trying the password reset.