How do I use this H/L/V Wiring?
I'm not sure why you have 3 switches, and only 2 12/2 cables. But I'll give it a stab anyway.

The fan unit should have 


1 Red wire.
1 Black wire.
1 Blue wire.
2 White wires.
1-3 Green or Bare wires.


The red wire in the unit should control the heat, so you'll hook the black from one switch to the red wire of the unit, and the white wire from the same cable to the white wire for the heater.

Next because you only have one more 12/2 cable from the switch bank, your light and fan will have to be controlled by the same switch. So you'll connect the black wire from the switch to both the black and blue wires on the unit, then the white wire from the same cable to the white wire for the fan/light.

If you want the other light to come on with the light/fan, hook the black wire to the light in with the black/blue wires on the unit, and the white wire to the light in with the white wire at the unit.



WARNING 

These instructions are for a typical installation, your situation may vary. Wire colors may vary from unit to unit, consult the manufacturers documentation for proper wiring diagram. Contact an Electrician before proceeding.