When you’re in the process of building the site, you wish to hide it from public and make it visible only after it’s fully created.
In this case you need Under Construction page where you’ll provide a time frame for when the maintenance will be done. It will also help you to avoid bad user experience while the site is incomplete.
So to create the maintenance page, you can use either WordPress plugin or install Jupiter demo template (some Under Construction templates are also included).
As for the plugin, you can use WP Maintenance Mode plugin.
How to install a plugin, you can read in the article Installing Plugins and Add-ons. Refer to the section “3rd Party Plugins Installation“.
WP Maintenance Mode plugin allows you as the administrator to have full access to your website during the maintenance mode. This means that you can see the working website and log in to your WordPress dashboard.
You can specify which user roles may be allowed to access the front and backend of the website while it is in the maintenance mode. By default, it is set to Administrator role only.
There are two Maintenance Templates you can install.
How to install demo templates, you can find in the article How to Install Templates.
When the template is installed, you can set its Home page as a front page in Settings > Reading, so your guests see the maintenance front page when visit the site.