I assume your app adds a script tag to the page. If so these are the two starter questions:
Without an example that will be a little hard to troubleshoot.
I have developed a site with react js for the Shopify app and created one public app using that site. Now when this app will be installed on the development store I want that my app will visible on that site but not happening now I haven't write any script that can you please help me with how to do this?
The UI of an app is intended for the store owners and not for its customers. Either as an embedded Iframe inside Shopify Admin or an external website that integrates with Shopify.