How much fun! You now have a new kitten to bring in the New Year! It can be a scary time for the kitten, however.
Below are a few tips to keep your kitten feeling safe and secure. Kittens easily adjust to one another. When you need to introduce a new kitten to your adult cat, be sure to make the introduction a gradual progression rather than an abrupt meeting. When introduced properly, adult cats learn to love their new little addition and will have fun romping with them, or at the very least, will tolerate them so that you all can live in harmony.
First, you will want to have a "home base" for the new kitten. Having his own comfort space is important so that he gets used to sights, sounds and scents within the home. You will find that your other cats may be curious and may even play "footsie" through the door with the new addition if you leave a toy near the door. You may hear growling or hissing as that is normal. The amount of growling and hissing should decrease as they become more used to one another. If you hear howling, it could indicate more time is needed and give them time and space they need to adjust.
You will want to move the kitten for a short time to another safe space to allow your adult cats to check out the new scent of the kitten. You will want to reassure your adult cat that the home is still his and that he is still loved and cherished.
Do not be impatient as it may take days, even weeks to get the two adjusted. Be patient and take it step-by-step. As you introduce them, be sure to give each his own alone time. By having them sleep separately, it allows for them to get rest and have reassurance that they are still the head of their domain.
You can begin to formally introduce by feeding and playing with both of them at the same time so they get used to being in one another's space. Be sure not to leave them unsupervised until you are sure that they are comfortable with one another. Be diligent because you do not want a serious altercation to develop. If one does develop, you will need to separate and begin the process all over again.