Will you be using both remotes at the same time (in one session)? If not then just select the activity you want and when you're done hit off. You could do that from either remote.

If you want to use them simultaneously you either have to select the same activity on the 2nd remote but hold your hand over the IR emitter on the top of the remote OR set up 2 activities - one that does everything (sets power and inputs) and one that does nothing but gives you the correct button mappings. The down side of option 2 is that you have to turn everything off with the same remote that you turned it on with.

Another option is to leave both remotes in the watch TV activity and use manual buttons to control the TV and receiver power and inputs.