This plugin is rather add-on to the mighty WooCommerce plugin and doesn't work on its own. So make sure you have WooCommerce installed and activated.

The plugin allows you to customize WooCommerce product archives. Change the number of product columns and the number of products displayed per page. Toggle the display of core elements and enable some that are not included in WooCommerce core such as stock levels and product categories. 

 The Product Archive Customiser Settings:

Please go to Dashboard > Appearance > Customize > Product Archives