How do you set the frequency and operate the #2VOR on the PC12?

This is what I found: you set VOR2 frequency on the second (the lower) GNS 530. Note that matter what you set, the lower GNS still displays VOR1 symbol, radial, distance etc, just like the top GNS. 

 

However, once you set the frequency you can play with the display on HSI and the VOR2 needle will respond, and you can make NAV to follow VOR2 too.

 

On this screenshot posted by Gregg:

http://forum.avsim.net/topic/453445-no-user-guide-for-pc-12/

 

The leftmost knob is for setting the VOR course/radial. The next two arrow buttons makes HSI to display VOR1 and/or VOR2 with two different arrows, but they don't switch the main navigation source between VOR1 and VOR2. Button "1-2" switches the main navigation source on HSI and on NAV between VOR1 and VOR2.

 

Plus, there is a second VOR gauge near main HSI you can set to show the current radials of VOR1 and VOR2.