Download the wp-orphanage-extended.zip file, unzip and upload the whole directory to the /wp-content/plugins/ directory
Activate the plugin through the 'Plugins' menu in WordPress.
Edit the plugin options to set the role you would like users to be promoted to, and other WP prefixes where to search for roles.
As an admin you can visit the Users page to automatically upgrade all orphan users of that blog to that role. Users who login before you do that will also get the same treatment (but only for their account).
Requires: 3.3 or higher Compatible up to: 3.9.1 Last Updated: 2014-4-19 Downloads: 1,722