To register your server with CloudLinux Network using activation key run:
$ yum install rhn-setup --enablerepo=cloudlinux-base
$ /usr/sbin/rhnreg_ks --activationkey= --force

Where activation key is like 1231-2b48feedf5b5a0e0609ae028d9275c93

If you have IP based license, use clnreg_ks command:
$ yum install rhn-setup --enablerepo=cloudlinux-base
$ /usr/sbin/clnreg_ks --force

URL of this page: https://docs.cloudlinux.com/index.html?registering.html