[Theme Horse Support Team]

Hi Shana,
First of all you just create a interface child folder where your interface pro theme is located. Both child and parent theme must be in the same directory. First import all the css from the child theme. And if you need to change code then create one functions.php file and first unhook the functions and then only customize the code.

For more info
http://codex.wordpress.org/Child_Themes

If you are unable to fix it then you need to hire a developer to fix the issue.

Thank you!