I don't know how you managed to install your software, my installation
contains a readme in english. There is
even a readme.es in spanish :-)
Did you find a subdirectory doc, it contains a lot of valuable information
that you might study.
If on windows try lisp.exe -B . -M lispinit.mem
on unix ./lisp.run -B . -M lispinit.mem
I can assure you that defun works