WordPress.org

1. Upload the files to the '/wp-content/plugins/plugin-manager' directory.
2. Activate the plugin through the 'Plugins' menu in WordPress.

To upgrade the plugin to a newer version

1. Deactivate the plugin.
2. Delete all the files under '/wp-content/plugins/plugin-manager'.
3. Upload new files to '/wp-content/plugins/plugin-manager'.
4. Activate the plugin.