None of my plugins are working (Bukkit + Hamachi)

Last 3 days ago, I've made my own Minecraft server by using Bukkit and Hamachi. It works fine for that I manage to do that part but then I wanted to add some plugins to it. I tried Essentials and I dragged the Java files into the plugin folder, then I run my batch file to restart the server finished restarting, but when I went on my server to try it out, the plugins weren't on, as if it never was installed, even though the folders and the plugins are all in the folder. I've been stuck with this problem for too long and I could use some help here.