Shopify Schema Markup for Reviews Widget is usually really complicated (since it is dependent upon the evaluation apps that you are using), I recommend you leave it into the experts.  Phase four: The module installation process is incredibly easy, how module configuration is effective might be witnessed within the demo https://www.presta-addons-modules.com/en/free-modules/prestashop-preloader-page-loading-image-page-loading-animation-preloading-screen-loading-page.html