Help required Noob here..PHP?

Hello everyone. How Exactly do I install PHP on a windows 8.1 operating system EVEN after following every step from YouTube Videos doing so? It's like my Laptop Doesn't want me to write php codes at all.. But why does stupid markup work from a plain notepad?? care to elaborate on this??

1)windows web developer-php installed 2)IIS active

Yet when I go to my browser and type local host/index.php with a correct saved file on the pup it sends out a html error...

(facepalm)