Login as the root user to SSH and run the following commands to install CSF:

wget https://download.configserver.com/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh

If you would like to disable APF+BFD (which you will need to do to avoid conflicts):

sh disable_apf_bfd.sh

Now, you can then configure csf and lfd in WHM, or edit the files directly in /etc/csf/*

To Configure the CSF Firewall

Go to the Home of your WHM dashboard and select the Plugins option from the navigation menu.

You will see the option ConfigServer Security & Firewall. Click on it.

Here, you will find a variety of options to configure the ConfigServer Security & Firewall application.

Click on the csf tab.

Scroll down a little to the csf – ConfigServer Firewall section and click on the Firewall Configuration button.

Configure as needed.

Disable Testing
Currently, your CSF application is running in the Test Mode. You have to deactivate the mode.

Reaccess the csf – ConfigServer Firewall section and click the Firewall Configuration button.
Locate the TESTING option in the Initial Settings section.
Click on the Off switch.