Have you considered installing Windows in a virtual machine such as VMWare Fusion for Mac?
If you need a native installation of Windows, but don't have a Windows PC, you can:
Option 1:
Download the Windows 10 ISO disk image to the Mac. Download and run
Balena Etcher to save it to a USB flash disk. Then boot from the USB flash disk (press F12 at BIOS splash screen).
Option 2:
Install the
trial version of VMWare Fusion and install Windows inside the VM. Then create a Windows 10 install disk by using Microsoft Media Creation Tool.
Disclaimer: I haven't tested these methods so feel free to try and let us know how it goes...