Creating a child theme is really simple. First, create a folder and name it by the parent theme (e.g., parentname-child). Next create a new file called style.css in your newly created folder. In this file, you should enter some information to identify it as a child theme:

/*
Theme Name: HBTheme Child
Description: Child theme for the HBTheme theme
Author: Your name here
Template: HBTheme
*/
@import url("../HBTheme/style.css");


And that’s it! Your theme should appear in your Appearance > Themes if you’ve made that folder in the wp-content/themes/.

For more information on working with Child Themes, please read up at http://wordpress.org.