WordPress.org

1. Upload the folder 'plugin-updater' to the '/wp-content/plugins/' directory.
2. CHMOD 777 /wp-content/plugins
3. CHMOD 777 /wp-content/plugins/plugin-updater/packages
4. Activate the plugin through the 'Plugins' menu in WordPress.

Note: Alternatively to steps 2,3 you can use "CHOWN -R {APACHEUSER} /wp-content/plugins" where {APACHEUSER} is your apache username.