Usually, the task of attaching bearer token to your call in Authorization header is taken care of by the built-in interceptor AdalInterceptor provided as part of package.
Please take a look at this sample. It works with Angular 6 and Adal-Angular-4 but should be pretty similar.
Authentication with Azure AD, Angular 6 client, Web API
Specifically the implementation of Step 3 in this article.
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule } from '@angular/common/http';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { AppRoutingModule } from './/app-routing.module';
import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AuthCallbackComponent } from './auth-callback/auth-callback.component';
import { AdalService, AdalInterceptor } from 'adal-angular4';
@NgModule({
declarations: [
AppComponent,
AuthCallbackComponent
],
imports: [
BrowserModule,
HttpClientModule,
AppRoutingModule,
FormsModule
],
providers: [AdalService, { provide: HTTP_INTERCEPTORS, useClass: AdalInterceptor, multi: true }],
bootstrap: [AppComponent]
})
export class AppModule { }
NOTE: You haven't posted any code for the part where you're making the http call. In case this suggestion doesn't help, please add the exact code and me/others can look for issues.