I recommend that you use a software like Photoshop or GIMP. GIMP is free, but, it isn't as easy to use, You have to pay for Photoshop but it is much more user friendly. I also recommend you go here to download a good template.
Its actually a nice amateur program, if you aren't the type to go for nerdy detail. It works well if you understand it and have a meticulous eye for perfection.
Made by paint and turned out better than I ever expected!
But apparently this dude just took someone's white skin, chose a color from the color picker dropper, and used paint bucket to click the white space. Hence the edgey edges