sendmail+cyrus+spamassassin

[Gordon]

I'm running RedHat 7.3 and I've got sendmail and cyrus-imapd working 
great. I'm also using sieve for some server-side sorting of messages and 
  I've set up squirrelmail so I can access it all over the web. Oh, and 
I'm using a couple dns blacklists with sendmail to keep most spam from 
even getting in.

The next piece that I'd like to play around with is integrating 
spamassassin (SA) in to identify the spam that does get through. The 
stuff that I've read has me somewhat perplexed in how to get this done. 
Does sendmail call SA before sending the message to cyrus? Does cyrus 
run SA? Is it something completely else? Anyway, how do I get SA to run 
in this configuration?

Gordon