Help with first spamassassin rules update

[Debian Newbie <debian@spamhole.com>]

Hello all

I am a newbie and have read through much documentation with no luck.  
We are running SpamAssassin version 3.0.3 (daemonised). I want to  
update the rules.

But when I type sa-update (bash shell, root user), I get "command not  
found."

Can someone help me out with the correct rules update command from  
the terminal. Currently my SpmAss rules are all held in /usr/share/ 
spamassassin/ if that makes a difference.

Thanks in advance! ;-)