Give them time separate to get used to the new sights and sounds of a new home/creature. It took 3 months for my cats to get used to my dog and vice versa. I was very strict about how the dog could behave around the cats, establishing leadership and ownership of the cats. Now they're fine with each other. My cats also lived with a high energy dog prior to adopting a new dog. My current dog has fairly low drive and spends most of his time cuddling and sleeping.