Erick,
Today, TE cannot perform the association that you're looking to do. However, the Vizia RF+ remote can. If you have one of those, you can go ahead and treat the device like a scene controller, and associate an area to activate to it in the settings menu.
As for the device not being added, could it be hidden behind the flyout bar? This is an annoying thing that ThinkEssentials does when adding devices sometimes, and we're looking at a way to fix it. Simply minimize the flyout with the Design/Scenes/Areas, and check to see if the device is there.