It's pretty easy to update server's kernel version in CentOS distro. Just run the command given below to finish the task.
# yum update kernel
However, we recommend to use -y flag just in case to secure vulnerability and to ensure you've the latest kernel in run.
# yum -y update kernel
The flag -y also replies 'Yes' to every question raised whilst the command runs.
Now reboot the server and confirm the kernel has been updated to the latest version by firing:
# uname -r
That's easy ! ;)