install ng2-bootstrap and bootstrap
npm install ng2-bootstrap bootstrap --save
open src/app/app.module.ts and add
import { AlertModule } from 'ng2-bootstrap/ng2-bootstrap';
@NgModule({
...
imports: [AlertModule.forRoot(), ... ],
...
})
open angular-cli.json and insert a new entry into the styles array
"styles": [
"styles.css",
"../node_modules/bootstrap/dist/css/bootstrap.min.css"
],