lilu dallas multipass

How does one acquire photoshop CS5?

I’ve just finished wiping my entire computer, so I don’t have any of my old programs and I’ve completely forgotten how to successfully install photoshop. I’m looking through tutorials and most just offer keygen and download links…but I seem to remember editing a host file or something last time. I USED NOTEPAD, OKAY, I REMEMBER THAT MUCH. Does anyone have instructions or a link or anything? I feel like a total idiot, but I would be so friggin’ grateful for any advice.