The last bit of the guide, flashing the kernel may not work for you and you may get the message ''cannot load elf kernel''. If so you need to use flashtool to flash the kernel:-
1. Enter fastboot mode on phone (plug usb and press volume up whilst phone is off)
2. Open flashtool and click flash icon (lightning symbol), select fastboot mode.
3. Click the 'Select Kernel to Flash' tab.
4. Search for folder where the kernel.elf file is, the file didn't show up for me but keep the location open.
5. Type the name of the kernel as the file name (should be U-DooMLoRD-AdvStkKernel-v01-test1.elf) then your phone should have root access.