How do I play campaign coop with a friend?

[bibaa]

Can someone explain how to play coop over plutonium? Thx in advance

[bibaa]

for anyone looking for answer, create lan lobby, choose coop, force the game to start solo by typing in console xpartygo, then your friend double clicks on your user under friends tab (f10) and thats it. If you need to restart type in console fast_restart