How do you turn Three Finger Drag on?

I'm trying to use the new "three finger drag" gesture in Lion and it's not working. There isn't a preference setting for it in TrackPad -> Point and Click either. Does anyone know how to turn it on?

Some older Macs only support two finger scrolling on the trackpad, not three. Since you're not seeing a setting for three finger drag, I'd guess your hardware just doesn't support it.

Are you able to do other gestures that require more than two fingers? If not, it's probably a hardware limitation, and you could just get a Magic Trackpad.

I've been trying to figure this out as well and found it on another site , so here you go:

System Preferences->Universal Access->Mouse and Trackpad->Trackpad Options-> then you have your choice of dragging with or without draglock :)

Hope this helps!

Source: http://hints.macworld.com/article.php?story=20110630003322997