Let’s see if we can make this as absolutely simplistic as possible.
Download winrar, from www.rarlabs.com. Install it. Once installation is completed, right click on the mame .zip archive. Choose ‘Extract All Files’. Click ‘OK’. This will extract it to a newly created folder on the desktop. If you like, you can move the folder to a different location, and create a shortcut for the executable (right click on the executable, and choose ‘create shortcut’, you can move the shortcut to your desktop if you so desire).
Hope that helps and makes it easy.