Sony xperia z c6603 resurrection

Hi, I'm unable to boot and stuck at this error when try to flash: "For flashtool, Unknown Sources and Debugging must be checked in phone settings". I have been able to flash DoomKernelv22 using fastboot, but can't flash ftf file becuase usb debuggin and unknown sources is not enabled and since can't get to boot the phone, i don't know how to enable those or force to install frf file somehow. please help thanks a lot