Hello,

Product page is the Woocommerce functionality. Here is the instruction on how to add the image: https://docs.woocommerce.com/document/adding-product-images-and-galleries/

By default, the image should be in Media Library. Our theme does not influence that.

Please install the theme on net WordPress installation and check if the image appears. If it do not, contact us.
Our support does not cover testing and fixing Knwat plugins, please contact them on this issue.

Best Regards