The Easy Way
In your WordPress admin, go to 'Plugins' and then click on 'Add New'. In the search box, type in 'SuperSlider' and hit enter. This plugin should be the first and likely the only result. Click on the 'Install' link. Once installed, click the 'Activate this plugin' link.
The Hard Way
Download the .zip file containing the plugin, unzip. Upload the Superslider folder into your /wp-content/plugins/ directory Find the Superslider plugin in the WordPress admin on the 'Plugins' page and click 'Activate'