Installing fastboot to pc -
To install fastboot follow the unlocking bootloader instructions as you will need the bootloader unlocked to be able to use and flash with fastboot once you have done that you will have fastboot on you pc already and can use it for flashing different kernals, software and recoverys. all these instructions are the manual way off using fastboot, NOTE- The new version of flashtool does have a user friendly automatic tool to flash software with fastboot if would prefere find out more on the flashtool instructions.
Flashing Kernals -
To flash different kernals on to your phones disconnect phone from pc first. Now move the kernal you want to flash to inside the fastboot folder then back out and open the comand propt window, enter this code ( fastboot flash boot boot.img ) and press enter. It will now say waiting for device now connect your phone while holding the search button make sure its completely off before doing this, it will now flash the kernal on to your phone when it has completed disconnet your phone and the new kernal will be installed.
To use recovery to flash zip files and perform nandroid backups plus more, you can either use a kernal with recovery built in or you can open one anytime using fastboot. To open using fastboot download this (Recovery) to the fast boot folder it might need extracting first. Before you start anything you must understand this is not a kernal or any img you can not flash it is only a bootable recovery if you do flash you phone will not boot up again. Now to get it working connect your phone while off and holding the search key to the pc when done open the command propt window and type ( fastboot boot recoveryPLAY.img ) then enter your phone should now boot into recovery so you can flash and backup and install root.