You can try to confront the offender. They might not be aware what they did was offensive. The victim can tell them their advances are unwelcome and ask them to stop.
You can also report the incident as soon as possible. Most victims blame themselves and are too afraid to come forward. However, the conduct might continue if it is not reported, and if management does not know about the incident, the business could be affected.
Follow company policy, and fully cooperate with management if an investigation is conducted. Be sure to make the complaint in writing. Be sure to document all sexual harassment incidents, such as dates, times, places, and people involved. Even eyewitnesses can report incidents.
If you report harassment to a person-in-charge and receive an inappropriate response, such as to ignore it, you can follow company policy to report the incident in another manner. You can also contact your county, city or town to see if they have any local laws to protect victims of sexual harassment. Physical harassment could also constitute a crime depending on the actions, so contacting the local police might be appropriate.