Basically if your juniper is kept inside, there is nothing to do for winter because it will not enter the dormancy which it needs. Outdoor conditions such as colder weather trigger dormancy in most trees, and if a tree such as your juniper is kept indoors, then it will not receive the signals that it needs to enter dormancy. If your juniper never goes dormant, it will tire out and eventually die. I'm sorry to hear that you have no place outside to put it. I recommend doing research on indoor bonsai species and giving away your juniper or planting it outside. Good luck!