Go to the Windows 10 download page.
Scroll down to the Download Tool Button and click it.
Once downloaded, double-click MediaCreationTool.exe.
Choose Create installation media for another PC
Uncheck the box if you want to change these options.
Choose ISO file
It will download your ISO
In the section Create a bootable disk using ISO Image, navigate to and select the Windows 10 ISO.
Click Start when your ready, it may take a while.