In this guide, we are going to see how to install a plugin. Before starting, you need to know that you can only install a plugin if your server is on Craftbukkit or Spigot. For example Vanilla, FTB, ATL or any Forge modpack doesn't accept any plugin. 

So please change your server version before beginning the tutorial from the "Maintenance" and "Reinstall" tab. 

An important thing, the plugin version must be compatible with server version. If you are on Craftbukkit 1.7.10, you can only install 1.7.10 plugin on your server. Otherwise it will be not loaded and you'll see an error message in the Console. 

1. So, to check your server version, go to the "Settings" menu and in the frame "Server Version" you can read your current                 version.  As you can see my version is Craftbukkit 1.8.8.

2. Now we can install plugins to the server, for this go in the "Plugins" tab and in the plugins list you can search the one you want. 

    When you'll be inside a plugin menu, you'll see multiple versions, so select the right one and install it. 

3. When the plugin is installed you can see it at the right frame. If you want to delete it, just click on the button beside, it will remove       the jar file but not the config folder. So, if you want to delete all the files, you need to connect with FTP access and Filezilla client. 

After the installation, you need to restart the server and if you wish to be sure of the installation, you can check it from the "Console" menu. If you see an error, change the version of the plugin or install missing dependency if it's required.