How do i access the assets in my asset pack (install-time)

Question

how do you access the assets in your asset pack (install-time)? I have made the assets packs but when i install the game, my game doesn't access them as i have not integrated any way to access the assets in asset pack.

i have made asset pack successfully (they have music files mp3)

i googled guide to include this code in my app MainActivity.java:

import android.content.res.AssetManager;
...
Context context = createPackageContext("com.example.app", 0);
AssetManager assetManager = context.getAssets();
InputStream is = assetManager.open("asset-name");

I have also made necessary changes to code

but somewhere this code gets error as i don't know at which location of the main activity should i paste it.

My MainActivity looks like this:

package com.monarchnexus.calmoasis;

import android.os.Bundle;

import org.apache.cordova.*;

public class MainActivity extends CordovaActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        // Enable Cordova apps to be started in the background
        Bundle extras = getIntent().getExtras();
        if (extras != null && extras.getBoolean("cdvStartInBackground", false)) {
            moveTaskToBack(true);
        }

        // Set by <content src="index.html" /> in config.xml
        loadUrl(launchUrl);
    }
}

(If that above code is not integrated in it )

Please suggest me a way guys, also tell me at which location in my MainActivity should i put that code