How do you file trespass charges?

"Charges" usually means criminal matters as opposed to civil matters. Go to your local police station and swear out a complaint charging the other person with tresspass. A policeman will help you with the paperwork. For civil trespass, you have to prepare an appropriate complaint according to the local court rules, file it with the court then serve it with a summons on the other person. A civil court worker probably will not help you prepare civil papers unless it is a small claims court. But every court is different, so check with yours.