How to change top bar when working with bottom navigation

I'm making my application based on the standard Bottom Navigation Activity from Android Studio.The code was generated automatically, I didn't change it.

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    BottomNavigationView navView = findViewById(R.id.nav_view);
    AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
            R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
            .build();
    NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
    NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
    NavigationUI.setupWithNavController(navView, navController);
}

And I have this: screen

I want to add to the top screen an icon, by which I will go to other fragments of the MainActivity (which are not in the bottom menu). I want to have this on top of screen top bar

How can I place them exactly on top?
How can I change the color of this top bar?

So far, I could only programmatically set the Title in onCreate MainActivity like this (after deleting labels in mobile_navigations):

this.getSupportActionBar().setTitle("TEST");

Solution

override onCreateOptionsMenu() in MainActivity.

 override fun onCreateOptionsMenu(menu: Menu?): Boolean {
     super.onCreateOptionsMenu(menu)
     menuInflater.inflate(R.menu.menu_second, menu)
     return true
 }

create menus in res folder

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/menu_next"
        android:title="toNext"
        android:titleCondensed="next"
        android:orderInCategory="1"
        android:icon="your icon"
        app:showAsAction="always" />
</menu>

menu api