WordPress Plugins are tools that offer added functionality to your application. To install WordPress plugins you simply have to put the plugin file into your "wp-content/plugins" directory. After it is installed, it can be activated or deactivated from the Plugins menu available in your WP administration.
The next step is to configure the installed plugin. The settings and procedure for this will vary depending on the plugin chosen.
Plugins can also be installed by using the upload option provided in the admin area. For this,the plugin must be downloaded from the source - a zip file usually - and upload it on your page using the add plugins option.