After purchasing a license from the cPanel Store for CloudLinux, you need to install it. There are multiple ways to do so, but the fastest way is to use CloudLinux's instructions, as provided below.
Verify that your license purchase has gone through and has been issued by navigating to our license verification page and enter your server IP address. If you have a CloudLinux license, it will show an entry in the list, as well as the logo:
License History for SERVER-IP
|active on DATE
Once you have verified that your license is active, log into your server via SSH and execute the following commands:
sh cldeploy -i
A reboot is required to boot into the newly installed CloudLinux kernel and finish the installation.
CloudLinux has a further explanation of their install process available here.