Couldn't be easier. Tiny program runs in the tray listening for connection request. When it gets one from the "Controller," it allows the Controller to take over. There is a plug-in for Firebox on the Controller end that makes the experience even more seamless. You as the controller can initiate a remote control session of the controlee computer and also open a chat window at the same time. (This is with the free version; I don't know what other bells the paid one has).