I am using QGIS and now GRASS GIS but I am not overly computer savvy. I am trying to add a GRASS modules (r.lfp) to my GRASS setup. I am on a Windows computer and can use the GRASS shell (I used to use .DOS in the old days). I've tried installing the extension using g.extension: it installs successfully (to c:/users/Bill/.grass7/addons) but also says that it won't function until the GRASS_ADDON_BASE variable is set. Can someone explain how I do that in simple language? I also tried to install r.lfp by saying "r.lfp -s" but perhaps I don't have permission to do so since that didn't work either. I've also tried to add r.lfp through the wxpython gui but the computer just hangs up and doesn't fetch the extensions repository (does it need something called numpy?)
g.gisenv set="GRASS_ADDON_BASE=pathtoyouraddondirectory" should do what you are after!
Note that the default setting is: "The default (...) on MS Windows $APPDATA\GRASS7\addons!"