Your site must be published to a URL before it can be mapped to a domain

Open your site and click the Publish button at the upper-right.

Enter a single word that has not already been used for a site name.

Do not try to use a URL. See the example below.

After editing your site remember to republish it.

You can take you site offline by unpublishing it and then republishing it when it is ready. 

To unpublish, click the down-arrow next to the publish button.

Publish your Site

Note: To use a web address that’s currently in use or has been used in the past for a site you own, change the address or permanently delete the existing site. Learn how to change the web address of an existing site. Learn how to delete a site.

Share your site

Check your sharing options

Choose who can see your site

See the Google Site help article

You can view Google Sites on a computer, phone, or tablet. When you edit your site, you must use a computer.