Please just follow this instruction.
Log in to your Shopify store admin
In Online Store > Themes > click Actions > Edit code
In Templates folder of your theme, find product.json file, it exists which means your theme is a Shopify 2.0 OS theme
After that, please install Ryviu widgets for your theme by following this instruction:
Note: Some shopify 2.0 OS theme is customized by developers so if you still cannot install Ryviu widgets, please just contact us so we can help you to install
All best wishes,