(1) Did you get the download from here...?...
https://www.microsoft.com/en-us/software-download/windows10
Download Windows 10 - currently, this is version 1803
Match it to your Edition (Pro, Home, etc.), Language, &
Architecture (x64/64-bit or x86/32-bit), as the article says.
(2) Did you boot to BIOS Setup & set it for UEFI, if you've got that...?...
https://www.sysnative.com/forums/hardware-tutorials/23010-get-access-bios-settings-boot-menu-f-keys-hotkeys-system-manufacturer-oem.html
Get access to BIOS settings & Boot Menu: F-keys/Hotkeys by System Manufacturer (OEM)
(3) Then plug in the USB Installation media & boot to it through the BIOS Boot Menu & select the UEFI option, if offered?
(4) Did you delete all the partitions at the "Choose a partition" screen, until only allocated space remained, select the unallocated space, & click "Next"?