After installing it press on the speaker and you will get the following screen.
Note - Do not play anything and have headphones plugged in when doing this
Now in order from top to bottom hit the circled buttons. After you press a button it will apply the mod to your phone and then on the bottom of your screen you will get a message saying "successfully applied to phone" or something. If you get a error message just try it again until you get the successfully applied message. Once you are done hit exit and you are done.
I tried this method when I was on the bus to see if it works, and surprisingly it did. I noticed a significant increase in headphone volume. I am not sure about the head set volume thou.