From the Editors of The Daily Cat
A cat tree is a great thing to have in your house. Location plays a very important role in whether your feline will ever use it, though. Since your cat most likely enjoys being near you, it probably would use the tree more if it were located in a family-occupied area. If you place it in the guestroom where no one goes, your cat will either ignore it or it will be forced to isolate itself from you, and that's something that neither of you would want.
The ideal spot is near a window in a room where your family spends time, such as a den or living room.