Open System Preferences
If you're using a Mouse:
Untick "Move content in the direction of finger movement when scrolling or navigating
If you're using a Trackpad:
Under "Scroll & Zoom",
Untick "Scroll direction: Natural"
At first I also hated inverted scrolling. But after awhile, I started liking it better. It doesn't make sense on a mouse with a scroll wheel -- but on an Apple trackpad, it makes more sense than the old school scrolling.