If you are new to React and using create-react-app cli setup, run the npm command below to include the latest version of bootstrap.

npm install --save bootstrap

or

npm install --save bootstrap@latest

Then add the following import statement to index.js file. (https://getbootstrap.com/docs/4.4/getting-started/webpack/#importing-compiled-css)

import '../node_modules/bootstrap/dist/css/bootstrap.min.css';

or

import 'bootstrap/dist/css/bootstrap.min.css';

don't forget to use className as attribute on target elements (react uses className as attribute instead of class).

Via npm, you would run the folowing

npm install bootstrap jquery --savenpm install css-loader style-loader --save-dev

If bootstrap 4, also add dependency popper.js

npm install popper.js --save

Add the following (as a new object) to your webpack config

loaders: [    {      test: /\.css$/,      loader: 'style-loader!css-loader'    }

Add the following to your index, or layout

import 'bootstrap/dist/css/bootstrap.css';import 'bootstrap/dist/js/bootstrap.js';

You can't use Bootstrap Jquery based Javascript components in React app, as anything that tries to manipulate DOM outside React is considered bad practice. Here you can read more info about it.

How to include Bootstrap in your React app:

1) Recommended. You can include raw CSS files of Bootstrap as the other answers specify.

2) Take a look at react-bootstrap library. It is exclusively written for React.

3) For Bootstrap 4 there is reactstrap

Bonus

These days I generally avoid Bootstrap libraries which provide ready to use components (above-mentioned react-bootstrap or reactstrap and so on). As you are becoming dependent on the props they take (you can't add custom behavior inside them) and you lose control over DOM that these components produce.

So either use only Bootstrap CSS or leave Bootstrap out. A general rule of thumb is: If are not sure whether you need it, you don't need it. I've seen a lot of applications which include Bootstrap, but using the only small amount of CSS of it and sometimes the most of this CSS is overridden by custom styles.