Go to FSX\CLS\CLS MD82\Manual\Operation Manual\3rd party weather radar integration (it is possible that I placed these folders/files there myself) and the way to integrate the CS Weather Radar into the virtual cockpit is on page 9.

Here I have copied the instructions for you:

Integration into the VC
To integrate it to the VC, you need to edit the panel.cfg of the MD-80.
The panel.cfg can be found in (starting from your main FSX folder):

../SimObjects/Airplanes/CLS_MD81/panel/

Open the panel.cfg in your favourite editor (Windows Notepad works fine)
and search for the section [VCockpit05] nearly at the end of the file,
search for the line texture=$M8WXR2 and add the following after it:

gauge00=WXR!wr_display, 80,32,350,275
gauge01=Captain_Sim.r001.P04!P04_radar, 0,0,512,382

Save it and the section should now look like this

[VCockpit05]
file=CLS_MD80_WXR_BG.bmp
size_mm=512
pixel_size=512
texture=$M8WXR2

gauge00=WXR!wr_display, 80,32,350,275
gauge01=Captain_Sim.r001.P04!P04_radar, 0,0,512,382

and the gauge should appear in the VC when you switch the selector knob
to position 2

Hope this helps.

Mark