res --> new --> Android resource directory.
menu->new->menu resource file (name as : menu_file.xml)
drawables -> new -> vector assests (choose 4 cliparts)

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menu_file.xml :

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/optionalmenu"
        android:title="Item"
        app:showAsAction="always"
        android:icon="@drawable/ic_baseline_menu_24">
        <menu>
            <item
                android:id="@+id/settings"
                android:title="settings"
                app:showAsAction="never"
                android:icon="@drawable/ic_baseline_settings_24"

                />
            <item
                android:id="@+id/about"
                android:title="about"
                app:showAsAction="never"
                android:icon="@drawable/ic_baseline_info_24"

                />
            <item
                android:id="@+id/exit"
                android:title="exit"
                app:showAsAction="never"
                android:icon="@drawable/ic_baseline_exit_to_app_24"

                />


        </menu>
    </item>

</menu>

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MainActivity.kt

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.widget.Toast

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.menu_file,menu)
        return super.onCreateOptionsMenu(menu)
    }
    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item.itemId){
            R.id.about -> Toast.makeText(this,"About Selected",Toast.LENGTH_SHORT).show()
            R.id.settings -> Toast.makeText(this,"Settings Selected",Toast.LENGTH_SHORT).show()
            R.id.exit -> Toast.makeText(this,"Exit Selected",Toast.LENGTH_SHORT).show()
        }
        return super.onOptionsItemSelected(item)
    }
}
