Please follow this instruction.
Log in to your Shopify store admin
In Online Store > Themes > Edit code
In Templates folder of your theme, find product.json file if 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 contact us so we can help you to install
All best wishes,