Jenkins auth plugin - where to store the script and how to pass parameters?

This is my first time dealing with Jenkins plugins - I apologize if it's too naive but I could not find an answer. Docs for this auth plugin, https://wiki.jenkins-ci.org/display/JENKINS/Script+Security+Realm, say: "Each time the authentication is attemped (which is once per session), the specified script will be invoked". However, it does not say where to put the script or what to name it. Is there a standard directory for plugin-related scripts in Jenkins or do I need to do some configuration after I write this script? Also, how can I get user parameters, id and password, on a login attempt? Any help is greatly appreciated.