WordPress.org

Installing this plugin, is just like installing any other WordPress plugin.

1. Download Advanced Custom Field Widget
2. Extract the /adv-custom-field-widget/ folder from the archive
3. Upload this folder to ../wp-contents/plugins/
4. Activate the plugin in Dashboard > Plugins
5. Customize from the Design > Widgets menu

In other words, just upload the /adv-custom-field-widget/ folder and its contents to your plugins folder.

For more information about plugins and installing them, please review the managing plugins section of the WordPress Codex.