After a reflash I transfer deb files including filebox to N9 from PC. Also a txt file which contains path to filebox. Next I will enable dev mode. Then from terminal I install filebox using the path saved in txt file (dpkg -i path). Txt file can be found from Documents app. From filebox I intstall other apps.

You don't need the txt file if you know the path already. Drawback is you still have to enable dev mode to use terminal.