that's actually a very good question. To answer it open the GPG app and search for them.
They don't show up in the search results, which seems to indicate that Google, or their devs, don't see them as games even though they have game-like elements.
Therefore, you would probably install them in the same place you install the other non-game apps. I guess that would be the store, since there's no "Google Play Apps" app?But they are games,
you'll probably say. And I might agree to a point, but right now they don't seem to be considered as such.