Author Bind

Author Bind is a plugin that lets you configure a User ID to override all future added or edited posts/pages. There is a settings page under Settings for this plugin where you can configure this ID. In addition, this plugin denies viewing author information in the browser. If you try to access any author .e.g. via http://..../?author=1 you will be redirected to home page. the same goes for perma links. The plugin also will override the error message when logging in to something generic, instead of informing the person trying to login if the username exists. This is currently only in english, and not translated.

Either download the zip, extract and upload the folder to /wp-content/plugins/ or install it from the extension market.