To add bootstrap in Angular CLI

npm install ngx-bootstrap --save

add index.html

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet">

for import component where you used:

import {NgbModule} from '@ng-bootstrap/ng-bootstrap';import { ButtonsModule } from 'ngx-bootstrap';

and import [ ButtonsModule.forRoot(),]

then, you can use the bootstrap component in your project..