Unfortunately I don't know too much myself about HR and Six Sigma, but I definitely agree that you need to research this some more before you finish you application and essays. If you don't sound like you know what you're talking about, it will not look favorably on you.
My understand of Six Sigma is that it is not actually implemented by HR, but of course HR has a huge role to play in the entire process. I would take a look at this article:
https://www.isixsigma.com/new-to-six-sig ... six-sigma/Also, it might not be bad to get a low level certification in Six Sigma (if possible) to help you not only learn but build you application. I wouldn't want to just jump into a career path before I knew what it was all about. Otherwise I woudln't know if I'd actually like it. What makes you want to do HR or get into six sigma? If you can answer that, then you app will be much better off.