My cat is 9 months male, we just got a 6 months female...please help?

The girl kitty is really nice, but our kitty is mean and hiss at the girl kitty, and the girl kitty hiss back at him, where they ever get along? They never have a cat fight, they just give warning, do you think it going to get better? I just give them both a bath now they just sitting there licking them selfs lol and staring at each other so innocent, just got the girl kitty last night. i hope they get along if not in 2 weeks ima give them to the shelter. I don't think the female kitty is spayed, is there a free vet i could go to in oregon?