How do I file a judgment on someone's credit report?

You as the landlord do not file a judgment. You can bring a law suit for back due rent and if you prevail, a final judgment will be entered by the Court. Credit Reporting Agencies pick up judgments from the public records so you do not have to report to anyone. If you are reluctant to get involved in a Court case, or do not want to spend the filing and other fees necessary to filing suit and go through the process, consider assigning the account receivable to a collection agency that reports accounts to credit bureaus. In this day and age, most reports to credit bureaus are done electronically by the major institutions and collection agencies.