To install ClamAV via the cPanel/WHM.login to WHM and in the cPanel section click on “Plugins” (Add-Ons in version 10) and ensure the checkbox for “clamavconnector” is checked then click Save at the bottom of that page.
If for some reason you do not see that option, check the box for “Pro”, click Save and try again .
Note, you will need to refresh your WHM interface to see the configuration options for ClamAV near the bottom of the list on the left.