In v88 we added ImunifyAV to the Security Advisor and a path to install from that user interface in WHM but if for example v86 is installed ImunifyAV needs to be installed manually.
The documentation and install instructions are located at ImunifyAV for cPanel
and the steps specifically to install manually are as follows:
wget https://repo.imunify360.cloudlinux.com/defence360/imav-deploy.sh -O imav-deploy.sh
bash imav-deploy.sh --key IPL