Watch a bunch of Jackson Galaxy videos. He has some great ideas. Often, aggression in cats is diffused by having places for the cats to get off the floor and spending time playing with the cats. He has great ideas on introducing cats and creating positive feelings when around each other. It isn't too late to start over and try again using his methods. It never seems like a good idea to have cats have nothing but each other to focus on. If you introduce play or treats around each other, they might learn to associate those good thoughts with the other.