node.js – Local host refuse to connect on my nodejs react file

I am just starting to run react on my local computer using node, and for that i first of all made html css and js files and in the js file, i used the following code

import React from “react”;
import ReactDom from “react-dom”;

ReactDOM.render(

, document.getElementById(“root”));

and for installing react i used cmd, and i wrote the following code=
cd (to my files directory)
npm install
npm start

after that it is showing that local host cant be found, what should i do?????