In Angular, you can call an API using the `HttpClient` module, which provides a convenient way to make HTTP requests. Here's a step-by-step guide on how to call an API in Angular: 1. Import the `HttpClient` module and inject it into your component or service. Make sure to import it from `@angular/common/http`. 

import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient) {}
2. Use the `http.get()`, `http.post()`, `http.put()`, or `http.delete()` methods to make the desired HTTP request. These methods return an `Observable` that you can subscribe to in order to handle the response. Here's an example of making a GET request to retrieve data from an API: 

this.http.get('https://api.example.com/data').subscribe(response => {
  // Handle the response data
});
3. If the API requires headers, parameters, or a request body, you can pass them as options to the HTTP request. For example, to include headers or query parameters, you can use the `HttpHeaders` and `HttpParams` classes from `@angular/common/http`. 

import { HttpHeaders, HttpParams } from '@angular/common/http';

// GET request with headers and query parameters
const headers = new HttpHeaders().set('Authorization', 'Bearer token');
const params = new HttpParams().set('param1', 'value1').set('param2', 'value2');

this.http.get('https://api.example.com/data', { headers, params }).subscribe(response => {
  // Handle the response data
});
4. For POST, PUT, or DELETE requests, you can also pass the request body as the second argument to the respective method. 

const book = { title: 'Example Book', author: 'John Doe' };

this.http.post('https://api.example.com/books', book).subscribe(response => {
  // Handle the response data
});
Note that the examples above are using the simplified version of making HTTP requests. In a real-world scenario, you would handle error handling, unsubscribe from the `Observable` to avoid memory leaks, and potentially use other options and features provided by the `HttpClient` module. Remember to import the `HttpClientModule` in your application's root or feature module to enable the `HttpClient` service. This is typically done in the module's `imports` array: 

import { HttpClientModule } from '@angular/common/http';

@NgModule({
  imports: [HttpClientModule],
  // Other module configurations
})
export class AppModule {}
By following these steps, you can easily call an API in Angular and handle the responses in your application.