Check the 'Create a Windows 7 or later version install disk' checkbox, and uncheck the 'Install Windows 7 or later version' checkbox. Here you will find the 'Boot camp' option.
Plug in your USB drive to the USB port, and make sure it has got a minimum of 8GB storage capacity. First download the ISO file to your Macintosh computer. If you're looking for a free Windows 7 USB/DVD download tool for mac then BootCamp can be said to be a greate choice. The Windows basically takes a certain partition of the mac computer hard drive installing the Windows separately on that selected partition, and the rest of the memory partition is allocated for macOS. With just a press of a button, you can switch between the mac and Windows platform swiftly. It allows users to burn Windows ISO to USB on a mac system. Bootcamp Assistant is actually a multi-purpose utility which has been incorporated on intel-based Macintosh computers by Apple.