First, you need to Login to your cPanel account. (Don’t know how to login to your cPanel account? Click here)
To set up an email filtering with SpamAssassin in cPanel. You will need to create a Spam folder within your webmail.
Locate and click on Email Accounts under Email section.
You will be redirected to the Email Accounts page, then just select the email account you wanted to create Spam folder and click Access Webmail.
Choose which email clients you wish to use from the 3 as seen on the image below.