First, download the kernel itself (probably from kernel.org, right?)
Then, follow the steps indicated here:
Basically, what you'll need to do is to unzip, then untar the kernel source. Then there is about 6 or 7 commands you type into the terminal to actually "compile" (build) the kernel.
If you are using GRUB as your bootloader, you'll then see, when you boot your system, that a new kernel is available for booting. Simply select that, and you should be running the new kernel.
Note these steps have to performed manually, i. e. without using yum or packagekit - but IMO will work better and give you more control over what happens.