Access to the courts is something guaranteed by the Constitution (standard disclaimer about the shape THAT's in). Usually googling "File a small claims case" and your state name will get you started. Here are the steps.
Answered like a librarian - with a link to an actual useful, authoritative resource. Perhaps YC can hire one to chip in to each discussion (I started typing that sentence tongue-in-cheek, but now I'm thinking that it would be fantastic. Imagine someone who added useful, authoritative resources to each discussion - rather than my having to skim through the crowd-sourced noise looking for the signal).