Add the following to your emacs initialization file to enable pymacs:

(autoload 'pymacs-load "pymacs" nil t)
(autoload 'pymacs-eval "pymacs" nil t)
(autoload 'pymacs-apply "pymacs")
(autoload 'pymacs-call "pymacs")

See http://pymacs.progiciels-bpi.ca/manual/index.html for
documentation on using pymacs.