Alright, interesting that it still works.
So like many other Java libraries, pIRCBotX uses Maven as a build-managing-tool. If you dont know, what you use software like this for: Imagine a Library, that uses other libraries aswell. You dont want to download 5 JARs and import them in your project. Also if a new version of the library you want comes out and it gets the logic of those other libraries itself, you would have to manually all remove them, download the new jar, import it, etc. If you use a tool like Maven, you have a file, where you specifiy dependencies(in your use-case the library). Maven then automatically imports all needed sub-dependencies. And if you want to change the version, you just change it in the one file and Maven does the rest. Of course there is more than that to it, but thats how it overall works, for a user like you. If you use an IDE like Eclipse or IntellIJ, you can already specify that a project should use Maven, when you create it. Then you just put this text in the so called pom.xml, which is a file that tells Maven everything it needs to know about the libraries you use. To then import for example pIRCBotX, you simply put this:
<dependency>
<groupId>com.github.pircbotx</groupId>
<artifactId>pircbotx</artifactId>
<version>2.2</version>
</dependency>
Between the <dependencies></dependencies>. Then it should already work fine