Step 1: app.module.ts file

import { HttpClientModule } from '@angular/common/http'  
imports: [
    HttpClientModule,
  ],

Step 2: data.service.ts file

import { Observable, of } from 'rxjs';
import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient) { }

  postUserSettingsForm(userSettings: UserSettings): Observable<any>{
    return this.http.post('url', userSettings)
  }