Step1:- Firstly, you need to plug in in your windows 8.1 bootable USB flash drive and restart your computer. Step2:- When your computer reboots, enter your system’s BIOS settings and you need to set your installation media. Now, you need to save your BIOS settings and restart your computer. Step3:- When your computer restarts, you need to press any key to boot from your installation media. You have to click any key to continue. Step4:- You will watch the succeeding loading screen with a circling progress bar. Wait for a few minutes till the compulsory files are loaded. Required any help, call at Windows8.1 Operating System Help number 1-844-200-0209 for instant help.