Hello pingram3541,
Thank you for your question regarding editing the functions.php, and style.css files for your BoldGrid site. You can do this with the most recent version of BoldGrid by going to the WordPress dashboard, hovering over Customize, and clicking on CSS/HTML Editor. From there you will see a drop-down list of themes that you have to edit, as well as the list of files for the currently selected theme.
I was not able to find an article, or write-up about using child themes for BoldGrid specifically, but we do have one for WordPress in general. However, please keep in mind that I’m not able to advise on the differences or limitations of using these instructions with BoldGrid in mind.
Gratefully,
Casey B.