Step1: What are the Hardware requirements of Windows 8/8.1: 

If you have hp company PC, then press f9 key when system starting ,

If you have dell company PC, then press f12 key when system is starting, 

If you have Acer company PC, then press f9 key when system is starting,

If you have Compaq company PC, then press f9 key when the system is starting.

Select your device where from you are going to install windows 8/8.1. If you are going to install from usb/Removable device then select and press ENTER or Using CD/DVD then select and press ENTER to continue to installation setup.
This windows shows that installation setup is starting now..
Select your own language and press ENTER or click on Next to continue installation setup. 

Now click on Install now button on screen and if you are going to repair old installed windows then press Repair your computer but we are going to install new windows. So click on Install now button.
This is the license screen of Microsoft windows 8/8.1. So, click on I accept the license terms and press on Next button.
Here click on Custom Windows only (advanced) and and you will see your computer hard drives.
Select your computer C drive and click on Drive options (advanced) button and then click on format button. This step will delete all data of your computer C drive and then press ENTER or click on Next button.
Actual process of windows installation is started now. Getting files ready for installation completes 100%.
System is rebooting now or you can click on restart now button or press ENTER from key board.
Configuring devices are attached with your computer system or checking drivers.
Enter your Computer name (PC) and select color scheme which you want.

Here select Use express settings.
Now your cursor to the right corner of the screen.
Getting ready your system for first use and this will take time.

Now your system is ready for use.