When you bring a new rabbit into your home, it's important to take some time to introduce them to your resident cat. While rabbits and cats can be natural buddies, they do need to be introduced gradually in order to give them both time to get used to each other's smells and presence.
The best way to start is by keeping the two animals separated at first, either in different rooms or using a baby gate. Allow them to sniff each other under the barrier and get comfortable with each other's scent before moving on to the next step.
Once they seem relaxed around each other, you can try letting them have supervised visits in a neutral territory, like a bathroom or laundry room. Keep an eye on their body language and make sure there is no growling, hissing, or raised hackles. If everything goes well, you can eventually let them have free reign of the house together!