With so many people adopting pets during the pandemic, there might come a time when you may adopt a cat while you already have another cat at home. To avoid potential problems, it’s best to introduce the new cat to your old cat carefully.
You might want to keep each cat separate but let them smell the presence of the other cat. Eventually you can let the two cats see each other through a barrier to keep them from attacking each other. When the time seems right (which translates to “never”), you can introduce the cats to each other and be ready to deal with screaming, hissing, and fighting. But that’s the joy of owning a cat.