we r looking for
“Disable driver signature enforcement”
1-Download and install Flashtool form here
2-do as what i say ( step by step )
after download the flashtool ....
now follow the steps :
Step 1: When you hit the power button in Windows 8.1 (through Charms Bar), hold down the Shift key when clicking the Restart button.
Step 2: The next screen will present you with three options. Click Troubleshoot.
Step 3: Next, hit Advanced options followed by Windows Startup Settings from the next screen.
Finally, you will be given a list of startup settings that you can change. The one we are looking for is “Disable driver signature enforcement”. To choose the setting, you will need to press the F7 key.
That’s all there is to it. Your PC will then reboot and you will be able to install unsigned drivers.
now After u done with that.......
Setup the flashtool and from it,Setup drivers .
then chose ur phone and 1stboot
then we r done