You can add a site password to your website for restricted viewing.
To do this, go to Site Settings on the menu page of your website.
Go down to where it says 'site password' and simply create a password.
This will now make your website restricted to viewing by only users who enter the password.
Please note that the layout of this page can be changed to suit your website and is available on any Plus Plan. Contact us at firstname.lastname@example.org to set up your own branded password page.