Just go to the TV device (Devices->Television) and the 4way should already be mapped. If not you can map them yourself. To get back to the activity you were in just press Devices twice. Of course this won't allow you to control any other devices. If you still want to control the A/V receiver volume or cable box at the same time then you'll have to setup a new activity. It's really easy - just make sure it uses the same devices as your Watch TV activity, then map the 4 way buttons to the TV instead of the cable box. In this case switching activities will have the effect of simply remapping the 4 way buttons (both ways). Power and inputs won't change.