We highly recommend that you change your password regularly. Whether that's once a year or once a month, changing your password is an effective way to reduce the chances of another person accessing your account.
To change your password you have two of the following options.
1) You can click "Forgot your Username or Password?" at the login page. It will take you to a page that asks you for your username or email address in order to email you a secure link that allows you to reset your password.
2) You may change your password from within the application at Settings > Change Password > Update Password.