I'm adding a walk in closet in what is now unfinished attic space. It will be attached to a bedroom in the finished side of the attic and it's above a living room. I need to "tap in" to existing wiring to add the switch and outlet, preferably the wiring from the bedroom so that it's on the same breaker. I have an idea of how this is accomplished, but I was hoping someone with experience could explain it so that I can be 100% confident with what I'm doing.