Hi: I just installed Antix 15 in a newer machine (the old one with 13 died), and I've been
busy setting it up. This one is wicked quick!.. __{{emoticon}}__

I figured out how to add application icons to the desktop in ROX-IceWM,
but cannot do so in Space-IceWM. Trying to drag and drop the desktop files
from the file manager yields an error message:
I get the same message as either my user or as root. Do I need to pinboard
ROX or SpaceFM to do this? How do I do so? I'd rather use Space as the standard
file manager.

Thanks in advance!

You could choose a space-icewm option for the session and copy the desktop files from usr/share/applications to ~/Desktop folder in the file manager (I like 2 pane view for that) and it should show on the desktop.