How do I add to the shortcut command line?

If you are using the retail version... Activision themselves said it like this:
"
To enable the console for the game:
1) Right-click on the shortcut you use the launch the game
2) Select properties
3) Make sure you are on the shortcut tab
4) At the end of the target line add -console, add this outside of the quotes
5) The finished line should look like this if you have the game installed to the default directory
"C:\Program Files\Activision\Vampire - Bloodlines\vampire.exe" -console
6) Hit ok, make sure you launch the game using this shortcut

"-from their guide on how to fix the leopold crash

Could also be some weirdness with Vista if you have that.