How do you put a judgment against a debtor?

You file a law suit, which means you notify the debtor. They may pay up rather than hire an attorney and going to court. If they don't, then you go to court. If they don't show up, you get a Default Judgement. If they do, the case is heard and the judge will issue a Judgement (presumably in your favor, if you have the debt properly documented).

You can then serve the judgment on the debtor to collect the amount. The judgment can be used to put a lien on property, garnish wages and other means of collection.