To use a Bootstrap navbar in an Angular app, you will need to install the Bootstrap library and include its styles in your app. Here is an example of how you can create a navbar using Bootstrap in an Angular app:

First, install Bootstrap by running the following command in your terminal:

npm install bootstrap

Next, include the Bootstrap styles in your Angular app by adding the following line to the styles array in the angular.json file:

"node_modules/bootstrap/dist/css/bootstrap.css"

Then, create a component for the navbar and use the Bootstrap navbar classes in the template:

import {Component} from '@angular/core';

@Component({
    selector: 'app-navbar',
    template: `
    <nav class="navbar navbar-expand-lg navbar-light bg-light">
      <a class="navbar-brand" routerLink="/">My App</a>
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>
      <div class="collapse navbar-collapse" id="navbarNav">
        <ul class="navbar-nav">
          <li class="nav-item active">
            <a class="nav-link" routerLink="/home">Home</a>
          </li>
          <li class="nav-item">
            <a class="nav-link" routerLink="/about">About</a>
          </li>
          <li class="nav-item">
            <a class="nav-link" routerLink="/contact">Contact</a>
          </li>
        </ul>
      </div>
    </nav>
  `,
    styles: []
})
export class NavbarComponent {
}

This will create a navbar with a brand name and a toggle button for responsive layouts. The navbar also has links for the “Home”, “About”, and “Contact” pages.

To use the navbar component in your app, you will need to add it to the declarations array in the module where it will be used. Then, you can use the <app-navbar> element in the template of any component to display the navbar.

Here is an example of how you can use the navbar component in a component template:

<app-navbar></app-navbar>
<router-outlet></router-outlet>

This will display the navbar at the top of the component, and the router-outlet element will display the content for the selected route.

For more information on how to use the Angular router to create a navigation system, you can refer to the Angular documentation: https://angular.io/guide/router. For more information on how to use Bootstrap with Angular, you can refer to the Bootstrap documentation: https://getbootstrap.com/docs/4.5/getting-started/introduction/.