You can use WiNToBootic even also if you don't have the. There are many applications available to create Windows bootable USB, I suggest you to use WiNToBootic. If you don't bother about formatting it, you can go with the former step. There is a workaround to make your USB bootable without formatting it. Frequent formatting of USB device will degrade its performance and why should you format your USB when you have more than enough space to make room for operating system files. Most of the applications available in Internet will format your USB to NTFS before making it bootable. Making windows bootable usb is simpler than it really seems. So, disable secure boot if it's not working for you. Though, it does not work in some devices.
Latest versions of some Linux distributions like Ubuntu and Fedora has the required signature in its boot loader to bypass the secure boot.
You have to disable secure boot in BIOS settings ( UEFI in your case) to boot from your USB. P.S: If you have bought a new PC or laptop and if it comes with Windows 8 or 8.1 (64-bit), you won't able to boot via USB. Access your BIOS and go to boot section and turn on removable storage booting or you can temporarily boot to USB by accessing boot devices options when your system starts. Note: To boot your system using a removable media, first you must correctly configure your BIOS settings.
