1) Login to your account/control panel
2) Click on the SYSTEM tab (top of the window)
3) Click on the domain you want to add an email address(bottom of the window)
4) Click on the MAIL icon in the SERVICES section.(center of the window)
5) Click on the email address you want to add the filter to
6) In the INFO section click the Spam Assassin link. (If Spam Assassin shows OFF, you must turn it on by clicking on the MAILBOX icon above and checking the ENABLE SPAM FILTERING box, then click ok)