It would be activated either by a Scramble Switch (plugged into black port on rear of VPro, I'm guessing this is an HKS part), another sort of momentary switch (wired to pin 25 or 26 of the VPro), or automatically (if the VPro is getting a speed signal from the ECU, to Pin 58).
If you have an HKS Mixture Controller then this can be used to set the launch control rev limit.
Whatever, when activated the orange LED on the VPro will flash.