WordPress.org

Installing is very easy and it should take no more than a few minutes.

1. Unpack the downloaded file in your /wp-content/plugins/ directory.
2. Activate the plugin through the 'Plugins' menu in WordPress.
3. Adjust the plugin options to your liking, then start creating your groups.

If you're upgrading from a previous version, just unpack the new version, overwriting the old plugin files.