Open impulse, right click on DG, and click "open application folder".  Once there, go into "bin".  Find "Demigod".  Right click and create a shortcut.  Move this shortcut to your desktop.  Once there, right click the shortcut and click "properties".  In the box next to "target", add /serverproxyonly so that it looks like

"C:\Program Files\Stardock Games\Demigod\bin\Demigod.exe" /serverproxyonly

You probably have a shortcut on you're desktop.

Use the Right Mouse Button (RMB) while hovering this shortcut and select Properties from the menu that appears

A window with properties of the shortcut is now showing.

The first edit control is called Target and shows something like "c:\program files\Stardock games\demigod\bin\demigod.exe"

after this text you need to add: /serverproxyonly

in this example it becomes:

"c:\program files\Stardock games\demigod\bin\demigod.exe" /serverproxyonly

Use the OK button to change the shortcut

Edit: LOL, use the description you like most