How to install WordPress plugins
Plugins add more functions to your site/blog. There are many plugins for a great number of different functions. Basically, they are all installed in the same way but different plugins may require some specific modifications before they become fully functional on your blog.
There are two ways to install WordPress plugins: with the Dashboard's built-in installer, or by downloading and uploading the plugin manually.
To use the automatic installer, log in to your Dashboard, go to Plugins>Add New, find the plugin you want and click on the Install Now link just under the plugin's name. Then to activate the plugin go to Plugins>Installed Plugins and click on Activate. Remember before that to read the details about the particular plugin because, depending on the plugin, you might need to do something extra to make it functional.
The second way to install plugins is to go to the plugins section of the official WordPress site, find the plugin there, download it to your local computer, unpack the archive and then upload the folder for the new plugin to the Wordpress folder on your hosting account, in the plugins directory: wp-content/plugins. Then activate it from your Dashboard and, if needed, make any additional modifications to make it functional.
For some more details and pictures you can also check our WordPress plugins tutorial.