New here and need some help please!

Hello, my name is Mikey and I have now 3 cats. We just got a new one today (yesterday) from a Petsmart adoption. However, we introduced them wrong and now everyone is scared of each other. No biting or fighting, just hissing. The two resident cats are sisters and are 9-10 years old. The new kitten is a 2.5 month old. We don't have a room we can separate the new cat in so that's not quite going to work keeping her in a room by herself. She's very outgoing and loving. My old cats are scared and not themselves at the moment. The one is bothered less by the kitten but still not happy. The kitten is going to the vet tomorrow but the adoption place had her there and she had a clean bill of health. She just needs her second round of shots I believe. She has already been de-wormed.

Thanks!!!
Mikey

Separation really is important while everyone is getting to know each other. Are you sure there's nowhere she could have for now? It's so important for her to have her own space so she can gain confidence in her new territory. Sharing your bedroom would be fine - it doesn't have to be a 'spare' room. It's not for long, in the grand scheme of things. Once she's settled you can progress to site swapping, so all the cats get some time in all the areas of the house.

If there really is nowhere, then another method is to use a big dog crate - the bigger the better - for the kitten whilst she settles in. It's not ideal for this situation (it's more often used when taming ferals), as a kitten really needs space for play.

Feliway diffusers could well help all the cats adjust to the changes, and Spirit Essences can be of great help too.

This situation can be resolved, but everyone having their own space really is crucial right now.

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Good luck, and enjoy your newest addition

Just thought I would add that all are doing well mild hitting but not bad and the two Older cats like to groom the kitten now

it sounds like things are going well. Be sure that the hitting doesn't escalate - you're taking a risk by not going through a slow introduction process.