Updating the kernel is just like updating anything else, e.g. yum update should do it (or whatever GUIish front end you prefer). The output should tell you if it got updated or not, rpm -q kernel shows you the installed kernels (by default, there should be 3 around for fallback). If it looks OK so far, reboot (teh new kernel takes over on reboot). Afterwards, uname -r tells you the release of the running kernel.