Since there is no direct "Download ARM" button on the consumer-facing Microsoft site, you must use one of the following methods.
If you own a device that came with Windows on ARM pre-installed, you can create your own installation media:
Most of these devices come with Windows 10 ARM pre-installed. If you are reinstalling:
Because most ARM devices do not have a traditional BIOS and rely on UEFI, creating a bootable USB differs slightly from x86 setups.