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,
Ryviu team