How to handle jealousy
If there's a new cat in the house, it's important that you cat feels sure that they aren't losing your attention or your affection. Spend time with them, play with them, and show them how much you love them.
Remember, too, that it's also very important for them to feel like their property is still theirs. Don't force them to share their food or water bowl, or their litter box. They may be ready to start doing it in time, but that should come slowly and spontaneously.
And whatever you do, don't go around giving love to their enemies like Ricky's human did!