Shouldn't be a problem - Campy don't use any unusual threading on their cranks. Grease the threads thoroughly, fit the end into the crank arm, reverse it round with the wrench til you hear a click, then go forwards. And don't forget that the left hand pedal is left hand thread.

If this doesn't help, try telling us a bit more about the problem. Do the threads engage but then you can't tighten them? Will they not engage at all? Are the cranks new, or used? Have you had any other pedals in them?