If you’d like to keep your site private while you’re working on it, you can use the Password Protect WordPress (PPWP) plugin, which comes pre-installed on the Arts & Humanities Portfolio template by default: the plugin makes your site (or certain site pages) available only to users with a password of your choosing.
Simply mouse over the Password Protect WordPress page from the left-hand navigation menu and click Sitewide Protection in the menu that appears when you hover. From there, check the toggle to enable password protection, set a password, and click the blue Save Changes button to save. When you’re ready to make your site public, simply uncheck the box.
Please note that while the plugin is active, site pages and content are not available publicly, but site Media Library content (such as images) are still accessible via their direct link.