Here's what I followed to get thus far:
How to Create a Child Theme
Create a directory in your themes directory to hold the child theme. The themes directory is wp-content/themes. You can name the directory whatever you want, but it is common practice to use the name of the parent theme folder with “-child” appended to it. So, for instance, if you are making a child of the twentytwelve theme, your folder name would be twentytwelve-child.
In the child theme directory, create a file called style.css. This is the only file required to make a child theme. etc etc
But now WP is giving me some uphill about the theme not being complete - see cut & paste:
CustomizeOPTIONS:WidgetsMenusWP-Creativix OptionsEdit CSSHeaderBackground
You only have one theme installed right now. Live a little! You can choose from over 1,000 free themes in the WordPress.org Theme Directory at any time: just click on the Install Themes tab above.
The following themes are installed but incomplete. Themes must have a stylesheet and a template.
WP-Creativix Child The parent theme is missing. Please install the "WP-Creativix" parent theme.
(But the WP-Creativix theme is clearly already installed and functioning well)