Howto exim + debian + sa-exim

I've done the following on debian sarge:

Installed exim-deamon-heavy, spamassassin, and spamc.  I've altered  
the resulting sa-exim.conf file in /etc/exim4 to enable sa-exim to  
run and set the debug level between 1 and 4 and seen nothing in  
exim's mainlog indicating that incoming mail in being scanned.

Please, please, please can someone tell me what I'm missing?   
Spamassassin is working, as far as I can tell.  I just need basic  
instructions on how to stop all this spam I'm getting.

Jonathan Hukari