WP-Lock turns your WordPress site into a private site. Only users with a login information can see the content on your site. Other users without any accounts will simply see a login screen. It also enables you to add a login screen message, to inform users that cannot log in.
- Download the plugin.
- Upload it via WordPress Admin > Plugins > Add New
- Activate it after installation is complete.
- You can change login message from the options page if you like.