Well until the OP responds and clarifies what he's actually asking there is no point in arguing about it.
Long story short, the default way to use XCI files does not "install" them internal or external. It adds waht is essetially a shortcut to the home screen and then you need to go to the SX menu to mount it before playing every time. As of 2.5.1Beta you can actually install them and run them like NSP files. I am not sure about installing them and running them from an external though.