Try separating them by a baby gate. That's what I did when I brought Fenway home to meet his new brothers, Cosmo & Maxie. I let them see eachother for about 1-2 days behind the gate. At one point I moved the cats in to where the dog was and moved the dog to where the cats were. They walked around and smelled and smelled and smelled these strange scents. Then after about 1 more day I opened the gate and they met. It was funny. Cosmo wasn't too sure about Fenway but Maxie made sure Fenway knew who wore the pants in the family.

I was actually very nervous about Maxie and wasn't sure if I would keep Fenway because my Neice once brought over her pug and Maxie freaked out (literally tried to climb the walls). It was sad to see. So I wasn't going to keep Fenway if Maxie was afraid of him.

Now Maxie beats Fenway up!

Good luck!