Most sexual harassers have victimized more than one person. Make it clear that you do not approve of his or her actions and that any repetition will be reported to a supervisor. This is not an easy step, especially if the offender is your supervisor, but it is important to let the offender know that his or her conduct is not welcome by you. If the harassment continues, report it to someone with authority to act. This may be a supervisor, a union steward, a personnel officer, or the owner of the company.
Many employers have anti-sexual harassment policies which include reporting procedures.
If so, use the procedure. Also, write a follow-up memo to the person to whom you spoke and keep a copy of yourself. Others may be victims, too, or may have observed what has happened to you. Sometimes other people are willing to help or complain themselves when they realize they are not alone. Talk to a private lawyer or to a staff member at the Idaho Human Rights Commission.