To enable the new SpamExperts filter you will need to login to cPanel and click "Professional Spam Filter" (SpamExperts) & log in.
If you have multiple domains within the same cPanel account you would then need to log in to domain you wish to use and it would be automatically setup on the spam cluster.
The only other thing you'll need to do is go to the "Email Routing" page within cPanel and ensure "Local Mail Exchanger" is selected.
Please note once the filter has been enabled it may take up to 2 hours for the system to start filtering your mail correctly.