Macs use the Audio Unit format (AU). Running a VST plug-in would require additional software ( a wrapper) as an interface to get the VST plug-in to work. From what I've heard, this is not a good work-around.
So Peter was having a bit of fun with your terminology. The correct term is an AU plug-in, not a VST plug-in.
You do this with "Controller Assignments", preferably in expert view.
1) open your plugin to see the interface on screen
2) enable learn mode in "Controller Assignments"
3) move the parameter of the plugin a bit by your mouse
4) move the fader or knob on the hardware controller and
5) switch learn mode off.
There are a couple of traps depending on the hardware controllers you use. But first try it as described, maybe it just works.