Select a cat you're compatible with. Bring it home and put it in a room (like the bedroom) on its own so it has a smaller space to adjust to - you should spend some time with it in that room. Both cats will know the other is there but keep them separated for about an hour or so. Expect a bit of hissing when they first meet, that's normal. Your first cat will try to establish who is boss in the household and make sure the new one knows that fact. They will adjust to the presence of each other in a few days.