Has your vet prescribed antibiotics? Treatment depends on the cause. If you haven't seen the vet you need to as soon as possible as congestion in our pets is almost always a serious problem. Some usual common causes are from something like aspiration, pneumonia, toxicity or even a heart problem.
You can't do anything for your dog at home. You need to take your dog to a vet and get him or her properly diagnosed and treated. You can't treat something until you know what the problem is. The problem may be more serious than congestion, for example a Heart Problem, Pneumonia an Infection, which would need Antibiotics to clear up, etc... Please don't put this off. You need to find out what's going on and the longer you wait to take your dog to the vet, the worse the dog will get and the more difficult it will be, to treat the problem. I hope it's nothing serious and that your baby is feeling better and back to normal soon.