How can I get my cats to get along?

I have a 1 year old Maine Coon who is sweet as can be. But last week a friend of mine moved & couldnt take her 5 year old Maine coon with her. So I took her. I put them in seperate rooms, etc.& tried to get them used to each others scent. Now, everytime they get withing 5 feet of each other they hiss & growl. I was just wondering if there is anything I can do to get them to get along better?