You need working python, reasonably recent version (such as 1.5.2).
If you use ordinary mailboxes (not maildirs), you need lockfile program,
which is part of procmail package. lockfile should be installed with
appropriate priviledges to be able to lock your mailbox - check out
procmail's documentation.

Copy pycmail executable somewhere (such as /usr/local/bin) and modify
the first line of it to point to your python interpreter.

Copy (and modify) pydfrc to /etc. Pay special attention to location of
sendmail and lockfile.

Put this into your ~/.forward:
|/usr/local/bin/pycmail

Some mailers need quotes:
"|/usr/local/bin/pycmail"

Edit your ~/.pycmailrc file. Look at examples/ directory for some examples.

!!! Always test if you still receive mails, after you make modification !!!
!!! to the configuration files                                          !!!

