Plugins are tools which provide additional functionality to your application. To install a plugin you generally just need to put the plugin file into your ‘wp-content/plugins’ directory. Once a plugin is installed, you may activate it or deactivate it from thePlugins menu in your WP administration.
Generally the Plugin installation is a straight-forward process. In most cases it is enough to upload the plugin under the ‘wp-content/plugins’ directory for the WordPress installation and activate it from the administrator backend.
In WordPress 2.7 and above you can install plugins directly from the admin area. Downlod the plugin to your computer, then log in to your WP admin area and go to Plugins > Add New. Browse to the plugin archive and select it. Then click Install Now and the plugin will be installed shortly.
The removal is also straight-forward in most cases. Simply remove the directory for the plugin you would like to uninstall and it will be automatically deactivated.
Still always bear in mind that not all plugins are easy to install, so always refer to their documentation and installation instructions first.