You enable file/folder sharing on the hard drive you want to share by
right-clicking on its icon and selecting "Sharing". That's if you are
sure you want to share everything on the drive. You may prefer to
mark only certain folders for sharing.
On the other computers, the shared drive or folders will appear in "My
Network Places". You can make a shortcut on the Desktop to "My
Network Places" or any of its contents if you like.