Problem using Boot Camp Assist

Hi,

I'm trying to install Windows 10 on a separate partition on my iMac.

Whenever I try and create the USB file using Boot Camp it says there isn't enough space on the USB drive.

Instead I've been following these instructions: Your Bootable USB Drive Could Not Be Created

When I get to the step that says to copy the contents of the ISO file to the USB I get the error message:

The Finder can’t complete the operation because some data in “bootsect.exe.mui” can’t be read or written.

(Error code -36)

Can anyone help with you I can avoid this error message?