Speed Graph Handle Curves

Hey everyone,

I'm still pretty new to After Effects and I've been practicing with animating AI. files. Something that I'm struggling with is the speed graph. I want to change the curvature of my graph to more of a "S" shape but the key frame handles won't move. The key frame goes up and down but I can't control the curve. 

Here's what I have now:

Here's what happens when I try moving the handles:

The first thing that comes to mind when explaining what I want to do is the pen tool. How you're able to adjust the curves by moving the handles around diagonally and what not. Like this:

My current keyframes are set to easy ease. How can I get the handles to move the same way as a pen tool handle?