How old is the kitten? If she is really tiny, you might want to isolate her in a room by herself like the bathroom where the other pets can't get to her while you are at work. Make sure she has food, water and a litterbox in there so you can keep track of what she is doing in there. The kitten will be shy at first and want someplace safe to hide.
When I brought home my two Siamese cats last month they hid under furniture for the first day or two then explored more as they got used to their new home.
When you are home make sure you give Fenway and Jojo plenty of attention but also give the kitten some time with you in a separate room. As the kitten feels more secure in your home then try introducing them while you supervise them.
Try catnip or a toy that both cats will be interested in, they may end up playing with each other instead of the toy. Good luck, don't rush things, they may surprise you and get along rather quickly once they get used to each other.