it is actually really easy with ROM manager.
open up RM, go to download ROM, find Chevyno1, Froyou Kernels, download the ones you want, or all of them.
go to install ROM from SD card, it will boot into clockworkmod recovery, go to install from SD card (not install update.zip) navigate to clockworkmod folder, and find the kernals, start with the ULV kernal of your choosing, and select it, go to yes and it i will install, then reboot. if it reboots fine, go to set CPU and overclock it to whatever you want it set at.
if you get stuck on M logo, pull the battery and boot into recovery (hold x and power yada yada yada) and follow the steps above to install .zip from SD and install another kernel. some phones like different kernals than others. i personally havn't had any real problems with ulv 1ghz, mlv 1ghz or the ulv 1.25ghz kernals from chevy on Bugless beast or chevys ROM's.
if you didn't understand anything i just said...just step back and do not go any further until you feel cumfortable with what i just said.