Hiyo frens! The easiest way to add this outfit on your skin is by using a program which allows you to make layers and transparent pixels, take Paint.net as an example. First, you open your skin in a skin editor and delete every part of the second layer. Once you're done, you open the desired program and open the png of the skin, without the second layer of course. It should look like something like the following:




Once you've done that, you make a new layer onto the texture.



Then, you paste the outfit into the second layer.



Once you're done with that, you merge the two layers by pressing the button and save the file, voila!

I hope that this helped you both (and everyone who's reading this) out, there also happen to be some videos online on how to do this.