Hide Inactive theme

I want to hide a parent theme from showing Under Appearance–>Themes.

I just want to show the child theme and hide the parent theme from showing at the adminstrative menu, how do I do that?

Also, where can i find the line in the wordpress files:

The template files are located in …. The stylesheet files are located in …. …. uses templates from …. Changes made to the templates will affect both themes.

I tried wp-admin/themes.php, but it’s not there.