adding completion file for zsh

["Andrei A. Voropaev" <av@simcon-mt.com>]

Hi!

Please direct me to some document that describes in plain words how to
add new completion file for use by zsh.

I have obtained _darcs from darcs website (yes I know newer version of
zsh has it bundled) and wanted to add it to the zsh 4.2.1 that I use. So
I've copied it to /usr/share/zsh/site-functions/

I know that zsh has found the file. First time I've messed up the
permissions so zsh complained that it can't open it :) But I still don't
have the completion. Yes, I have completion for all kinds of stuff and
where I use new zsh I also have it working for darcs.

Do I need something else to do? Or the file I got is simply incompatible
with 4.2.1 completion system?

Sorry, probably I could have figured out myself by digging in
documentation, but I really hope for quick answer here :)

Thank you

-- 
Minds, like parachutes, function best when open