Kernel Flashing Guide

First Method

1. Download the kernel zip.
2. Reboot to recovery. This assumes you have a working custom recovery. Please visit this section for list of recoveries.
3. Flash the kernel zip from the recovery, just like how you flash a ROM.

Second Method

1. Donwload the kernel zip.
2. Extract boot.img from the kernel zip.
3. Boot the phone into bootloader (fastboot).
4. flash the boot.img:

fastboot flash boot <drag and drop the boot.img>

Note

This actually works for recovery as well. For the First Method, you can just flash the recovery zip.

As for the Second Method, replace boot with recovery, and drag-and-drop the extracted recovery.img instead.