Begin the process by logging into your WHM using the root access:
Once logged into the WHM navigate to the WHM Marketplace
Click the Manage button next to the cPanel & WHM icon
Click on Add a Product and pick Partner Add-ons
From the available dropdown pick the KernelCare and enter your server IP.
The final step is to review and checkout the purchase, ensuring that you have a valid method of payment stored on the account.