sendmail config query

[Chris Richards]

Hiya,
 
I am running FreeBSD 5.1-RELEASE-p10 and want to configure
SMTP-AUTH/TLS. A friend gave me some instructions on how to do it and
they talk about editing "$SRC/devtools/Site/site.config.m4" $SRC being
the sendmail source of course. My friend is not a FreeBSD user so I
can't ask him for help.
 
I just have a standard install of sendmail on a normal system build. Can
someone point me in the right direction as to where this file should be?
I have searched for it and it does not exist in the current system - Is
there a directory somewhere that I can add it to so it will be included
in a sendmail build?
 
Thank you for reading and hopefully responding.
 
Cheers,
Chris