This plugin is a Comment Link Management Tool for follow and nofollow links to be used as an addon for Nofollow Case by Case or NFCBC SEO Light. Manag
Download the plugin archive and expand it (you've likely already done this).
Put the 'nfcbc-seo-plugin-add-on.php' file into your wp-content/plugins/ directory.
Go to the Plugins page in your WordPress Administration area and click 'Activate' for NFCBC SEO Plugin Add-on.