This tutorial shows how to enable Password Protection for Shopify frontend.
In order to protect the store frontend with password, navigate to Shopify admin panel and open the Settings -> Online Store tab.
Check the Storefront password option. You will see the Password field, you can leave password as it is or replace it with yours:
In the Message for your visitors field, you can add custom message that will be displayed to site visitors while site is under construction.
Save the changes and check the site home page. It will be password protected. To preview the site, enter the password from the Storefront password field of admin panel:
Disable password protection by unchecking the Storefront password option in Shopify admin panel.
Feel free to check the detailed video tutorial below: