If you have a controller that actually sends 14 bit MIDI, you can use it by enabling the 14 bit toggle, like Zoltan posted before.
If your controller does not actually send 14 bit MIDI, that button does not magically make your controller do so.
The combining of two CCs doesn't mean that you will be physically turning two knobs on your controller. On a 14 bit CC, your controller will read out the (stepless) value of the potentiometer of a single knob and quantize it to 14 bits. It will then send out the MSB on the first CC and the LSB on its paired second CC. By enabling the toggle in Resolume, Resolume will know to combine the value of that shortcut's CC with its pair CC, and calculate it back to a single value. That value is then used to set the parameter you assigned the shortcut to.
So on one side, you're turning one knob, and on the other side, you're seeing one value change. Aside from the higher range, there is no physical difference from a regular 7 bit CC.
Does that help explain it?