You already have a bootable flash drive.
How to do this is described in this article
Boot from a flash drive.
How to boot from an external USB device is written in this article
1. After you first boot the computer you’ll see a screen like this one. Choose the OS’ language, time and currency format, and input method.
2. Click Next and you’ll be taken to the Install now button screen. Which obviously you should click.
3. Enter your Windows 10 key, then click Next
5. Select type of installation. As we are doing a clean install, we should choose the custom install (files, settings, and apps aren’t moved).
6. At this point you’ll need to pick where to install Windows 10. You might need to delete or create a partition.
7. Wait while Windows installs. This process may take anywhere from half an hour to several hours, depending on your computer’s previous operating system and processing speed.
After the installation is complete, the computer will restart, do not forget to remove the boot from the flash drive or you can just pull out the flash drive.
8. Windows installation will begin. The computer will reboot.
9. Choose your PC name and personalize the color.
10. Here you can choose express settings or choose customize. I accept default settings and click “Use express settings”
11. Create an account.
12. Choose finish to continue.
13. Once the desktop has loaded, right-click on start-Select System
14. In the pop-up window, click Activate Windows.
15. Click on Activate or Enter Key.
IMPORTANT! You must be connected to the Internet!
16. Congratulations your Windows is activated!