To begin:
npx create-react-app my-app
cd my-app
npm start

Delete all default mark up.

For components create folder #components in #src folder and place there your react components. In my project you can see: Form.jsx, FormInput.jsx, List.jsx. You can create as many components as you want and name it how you like.

In this project Material-UI is used. To install run:
npm install @material-ui/core

Material-UI was developed based on the Roboto font. The Roboto font will not be automatically loaded into Material-UI. So be sure to install it.

To install run:
npm install fontsource-roboto

Then import it in "index.js". To do so write in "index.js":
import 'fontsource-roboto';

To use icons run:
npm install @material-ui/icons

Button example:

import React from 'react';
import Button from "@material-ui/core/Button";
// custom styles with Material UI
const useStyles = makeStyles({
 root: {
 background: 'linear-gradient(45deg, gray 30%, black 90%)',
 border: 0,
 color: 'white',
 height: 30,
 padding: '0 10px',
 whiteSpace: 'nowrap',
 margin: '15px 0 0 20px',
 }
});
const Button = () => {
 const classes = useStyles();
 
 return (
 <Button
 type="submit"
 alt="add-note"
 className={classes.root}
 >
 Add task
 </Button>
 )
 
export default Button;

Then you can see the result - button "ADD TASK" look like:

Button example

That was easy, right :)