site is down and want to restore all wp default settings

[Teke]

I messed up my account by messing with my magazine theme's style.css file (bad idea) and
my website is down: www.digitalfordealerships.com.

Wordpress admin is not even allowing me to install a theme as I get the following error:

Unpacking the package…
Installing the theme…
Could not create directory. /home3/digitec4/public_html/wp-content/themes/genesis/
Theme install failed.

I would like to cut my losses short and start from scratch with a functional default wp admin dashboard. How can I restore to default so I can download a fresh new child theme?