We just got a new cat and....?

anright he is 3 or four mounths we got him from last chance rescue. he and our dogs get along, my our current car luna she hates him! she hisses and moans. But he will just lay there and pur while she does so he dosnet have a problem with her. How long will it take for them to become friends and what should we do to make it happen. btw there both fixed