You can use the ILLiad client and follow the instructions for Changing User Passwords, or the patron can click on the "Forgot Password" link on the logon page to reset their password.
Both the logon.html and logon2.html pages by default have a forgot password link. If you are not using ILLiad Authentication, or ILLiad Exclusive Authentication, the forgot password link should be commented out or removed in your coding.