Where and how to include a custom .cf to spamassassin?

Hi all,

I want to include some extra spam rules and more specific those from Kevin A. McGrail.
The full ruleset consists of 4 cf files: KAM.cf, nonKAMrules.cf, KAM_deadweight.cf and KAM_heavyweight.cf.
Where should I place them and how to include them to spamassassin?

I guess it should be under /etc/spamassassin/ but can someone confirm please?

Thanks in advance