Thanks for thatYou can also use
adb push C:\path to file\file.txt \SDcard\directory
I was able to move some XBMC add ons this way.
There is a whole page on the Kodi wiki on FTV
http://kodi.wiki/view/Amazon_Fire_TV
Embarrassingly I missed the bit on copying files. Now found by searching the page using HecFam's hint.