WordPress installation isn’t linked to the operating system of your computer. WordPress is a Linux app running on a server, either at WordPress.com or your own hosting service.
It sounds like you’ve got your own hosting, so the upgrade files would need to be uploaded to that server. In other words, you need to be able to access the WordPress files on the Yahoo server for your account and have the ability to FTP the upgrade files to the server.
The files on your Mac don’t do anything.