There are two methods to legitametly obtaining a Windows 10 ISO file from Microsoft. First is the direct download option, however the link typically is changed multiple times a year so the website may not function properly. Microsoft encourages the use of the Windows 10 Setup tool instead, and here's how to use both options.
Create a Windows Install USB with Rufus Requirements: A Windows PC, a Windows 7+ ISO file, and a 4+ GB USB drive
First, download Rufus. It is a utility that helps format and create bootable USB flash drives, such as USB keys/pendrives, memory sticks, etc. and is significantly faster than Unetbootin and Windows 7 USB/DVD download tool, alongside being more versatile.
Visit https://rufus.akeo.ie/ and download the top file under the Download header. It will download as an executable file and double click it to run.
Above is what Rufus will appear as when it is first opened, however, this configuration will most likely not work for you.
Select the device you want to put the Windows ISO on, in this instance, my 64GB USB stick is my E: drive. Choose MBR partition scheme for BIOS or UEFI-CSM, this allows the USB to work with UEFI and BIOS machines (pretty much any computer made in the last 15 years). Then, most importantly, the file system must be NTFS. This is so the Windows installer work…
Thanks to an amazing member of the Apple community, AppleBetas, a fantastic website called the Beta Download Center exists and links to the iOS, macOS, watchOS, and tvOS beta profiles that can be installed on-device easily. After a reboot the beta software will be available for any of the compatible devices!