As of Windows there has been increased security & thus it blocks all unknown driver installations, So here are some steps to install drivers by disabling driver verification in Windows 8.
1. Go to setting(move your mouse to right side of screen you will find setting below)
2. Select the Change PC Settings option.
3. Click the General section option
4. Now scroll down to advanced startup & click Restart now below in Advanced Startup (after this pc'll go in advanced startup mode)
5. Then click here on Troubleshoot option
6. Go to start up settings
7. Click restart
8. It will reboot
9. Now you will have a bunch of options at the startup screen.
10. Now choose 7th option which will be disable driver verification (Choose it via num-pad)
11. It will restart
12. Now install the drivers you need to install
13. Restart your PC again
I have a detailed video of this procedure below.