1.run commnad in cmd
npm install bootstrap --save
2.after install add this to index.js
import 'bootstrap/dist/css/bootstrap.min.css';<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>{/* The following line can be included in your src/index.js or App.js file*/}
import 'bootstrap/dist/css/bootstrap.min.css';npm install --save bootstrapCopyimport 'bootstrap/dist/css/bootstrap.css';// Put any other imports below so that CSS from your// components takes precedence over default styles.Copynpm install bootstrap --save // Inside of your command line
import 'bootstrap/dist/css/bootstrap.min.css'; // Inside of your index.js