All apps should have a README file in them that will take you through the install, setup and anything else you need to know. This app also has online documentation. docs.splunk.com/Documentation/OPSEC-LEA/latest/Install/Checklist
One thing I did notice with this app is they recommend installing ithe LEA-Loggrabber on a Lightweight forwarder and not a Universal forwarder so you can use the UI to configure it. If this is not possible for some reason, I'm sure any of the splunk partners would be able to reverse engineer the setup files and manually configure it for you.
