I wanted to create a custom bbPress theme

Wordpress version: 3.6
bbPress 2.3.2
Site url: http://www.rubycore-ng.com/blog/forum/

I wanted to create a custom bbPress theme, i followed the instructions here:’ Step-by-Step Guide to Creating a Custom bbPress Theme’. Having copied the following assets from the bbpress>template>default folder to my child theme:

1-bbpress folder
2-extras folder
3-js folder
4-bbpress-functions.php

I am still unable to override the styles in the default bbpress.css file.

I would appreciate clues on how to approach this.

Regards.