Just make sure there is plenty clean, fresh water available. Obviously if it gets more serious than a cough, you need to see a vet; but usualy it will clear up in a week or two, just keep an eye on the dog for more serious symptoms, runny eyes, shivering, hight temp, etc. But for just a cough, don't worry to much... rest and cleanliness should do the trick. Hope it gets well soon.
Cheers.