If you know how to access device with WinSCP (over wifi) its really easy.

Connect to N9 via WinSCP
Open the FDBT install script
Do what the script says, but manually thru WinSCP file explorer


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If you can only use xterminal:

(for original theme)
copy "fdb-original" folder to MyDocs (to root of device in storage mode via PC)
open xterm and :
[become root]
cp -R /home/user/MyDocs/fdb-original /usr/share/themes/