Well if it is a bouncy or active dog I would take it very slowly - smelling through a door so they get use to each others smells before they see each other, and in the mean time teaching the dog some manners. Then, with the dog on a leash, have them in the same room. If you can get the dog to sit and let the cats come up and smell it, so much the better, but expect there to be spitting and claws on the cats part, and a wish to retaliate on the dogs part (hence the need for a leash). If it is a big dog, then getting a halti will help you restrain the dog and they also act as a muzzle so will minimise the risk of damage (to the cats at least). Shadow was only four months old when I got him, and a deeply depressed puppy, so did not react badly at all. He just assumed he was bottom of the heap and has remained there ever since. Other dogs it is not so easy. Bimbo, my hound dog had always chased cats so when introduced to a five week old kitten wanted to eat it. We introduced them through the sceen door (one that was also a security door so had wire mesh as well as the flywire). Bimbo threw herself at the door, the kitten fluffed up and hissed but stood its ground, and after a few days all was peaceful on the home front again ...
