How to create an OpenFire plugin

I am very new to java and feel very confused. I am trying to create a VERY basic plugin for an OpenFire server, but I don’t know how to get started. I read the Developer's Guide, but it does not explain how to configure everything in eclipse. Do you have good tutorials on how to create plugins for other applications in java? For example, how do I import all openfire classes? I get errors for all of these lines of code:

package org.jivesoftware.openfire.plugin; //error is: The declared package "org.jivesoftware.openfire.plugin" does not match the expected package ""

import org.jivesoftware.admin.AuthCheckFilter; //errors are: The import org.jivesoftware cannot be resolved
import org.jivesoftware.openfire.MessageRouter;
import org.jivesoftware.openfire.XMPPServer;

My background is in C #, so the syntax looks almost identical, but I have no idea how to use eclipse or how java works for plugins (it seems very different from DLL).

Thank you very much!