1. First of all, insert bootable USB drive or Window CD / DVD on Machine.
2. After inserting the drive then press F2 or F9 or F11 or F12 & select USB Storage device.
3. Choose the Language for window installation and click Next.
4. Now, one new screen appear just click on Install Now.
5. Further its asked for Window Product key, here usually just click on Next.
6. Admit the License Terms and click on Next icon.
7. Now install window through Custom.
8. Just select a partition drive where you want to install Windows 8 and click Next.
9. After 5 to 10 minutes window installation process completed and screen appear for Restart Machine.
10. Now remove bootable device from the machine and do some setting according to windows requirement like Theme Color, PC Name, Adding E-mail account , Set Password.
11. After all of these basic requirements, you just use your Machine.