I completed an online React course and deployed my application to Heroku. During development, I used the 'json-server' module found at https://github.com/typicode/json-server. This served up a folder on my computer which contained a simple json file and a few images for my website while conforming with the REST API. What do I need to do to get the server to operate independently of my machine so that my application can fetch the data ? I have zero experience doing this.
if you mean you want to create a server for your site,
first of all, you need to get a server, which can run nodejs , then you need to deploy and run your JSON server via a nodejs(express) app.
then you can connect to your server via your website/app
in order to do these things, you can follow tutorials
there are lots of tutorials about it.
hope you got the idea.