You already have a bootable flash drive.
How to do this is described in this article – Create Bootable USB Drive
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. Click Next
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. Installation process
9. Select your Region. Click the Yes button..
10. Select your keyboard layout. Click the Yes button.
11. Click the Skip button, unless you need to add a second keyboard layout.
12. Click the Set up for personal use option.
13. Sign in to your Microsoft account or select Offline account. If you don’t have a Microsoft account, you can create one right away. Alternatively, you can sign in with a local account.
14. Create an account. You can skip this step and do it later.
15. Create a password
16. Click the Create PIN button to set up a PIN to unlock your device.
Quick Tip: If you prefer to use a traditional password, click the Create PIN button, and then click the Cancel button to skip the process.
17. Create your new four-digit PIN. (If you want to create a complex PIN, you can check the Include letters and symbols option). Click the OK button.
18. (Optional) You can enter your phone number and then click the Send button to link your phone with your device, but this is a feature that you can set up some other time. If you want to skip this option (recommended), click the Do it later button in the bottom left corner of the screen.
19. Choose privacy setting. I accept default settings.
21. Once the desktop has loaded, right-click on start > Select Setting.
22. Click on Personalization.
23. Click on Desktop icon settings.
24. Tick the box next to “Computer” and click Apply
24. Right-click on This PC > Properties.
24. .Congratulations your Windows is activated!