Cannot see INSTALL for freshly purchased Steam games

Many times my Ally is placed near my desktop PC and they are in the same WIFI network. After I have purchased some games in desktop PC Steam client, I immediately see these games appear in my Rog Ally Steam library. But I only see STREAM button there and not the INSTALL button. Why is that? It seems the Steam client in Rog Ally thinks I want to stream play the game from my desktop PC, it is NOT what I want. I want to install the games locally into my Rog Ally. So what should I do besides to manually EXIT the Steam Client in my desktop PC?