[Exim] exim + spamassassin + filter file - howto

hi all,

kinda hit a brick wall here... i have installed spamassassin with exim. and it works well.

there was deb package that i installed. i also put in the necessary transport and director bits in the exim.conf file. to make it all work.

emails now sent to anyones mailbox will be stampped with relevent info ie X-Spam-Status: etc etc....

my question is how to implement a filter file which the docs recommend to do ...like the following...

if
    $h_X-Spam-Status: contains "Yes"
        or
    "${if def:h_X-Spam-Flag {def}{undef}}" is "def"
then
    logwrite "    => junk : SPAM"
    save $home/Mail/junk/spam/
    finish
endif

i understand the principle of what the code does. what i am not sure how to do is how to implement this code. using a filter file.

how does this tie in with exim and its conf file and .forward files and/or directories they are meant to reside ? etc etc ?

any help or guidance is muchly appreciated.

thanks all :)

best regards

chris g