Please download zorka child theme here or http://support.g5plus.net/wp-content/uploads/2015/09/zorka-child.zip, then replace current on your hosting/server.
After that, you can write style in child theme folder.
If you have any troubles configuring your website applications with the above settings you can contact the Support Center by signing up and submit a new topic. G5Theme Support Team will be glad to assist you.
Thank you very much for choosing G5Theme!