They way to do this, is to zoom into your clip in your timeline (stretch your V1/V2 lines etc higher if need be so you can see the white line through your clip) Click on the FX button at the top of your clip, and select Motion > speed. That line is now your speed, Click here for screen shot8149_screenshot20141028at10.58.12am.png.zip
You can add markers by holding down command (if your using mac) to get a + on your pointer, and can increase/decrease speed between markers. Drag your prongs apart at the top to gradually in/decrease speed ramp.
This make Sense?