Flexx Child Themes
Child Themes for the Flexx theme
In order to preserve your original theme, you can use Child Themes to apply modifications to your Flexx theme, without having to modify any of the original theme files.
Download one of the child themes for Flexx listed below. Unzip and upload the child Theme to your themes folder, and activate it, just as you would activate any other theme. There is a README.TXT included in the child theme with further information.
As an addon feature, the child themes enable the use of featured posts images, or post thumbnails, as described in this article. Featured images can be added using the featured images option on the write post panel.