tl;dr- it's a Hystrix reporter for SLF4J loggers
Skim through this post if you're curious.
You'll need Maven and JDK 7+. mvn clean package will download everything and build a JAR for you. Assuming you're using a dropwizard app, dropping in the reporter is as simple as adding the dependency and this line to your run() method:
environment.lifecycle().manage(new LogentriesReporter());
Actually, there's not much more to it than that!