Hi dmozi313,
Yes, if the file doesn't exist create it and add the CSS code with nothing else right.
and if it exists add it to the end of the file.
About the title of the Categories that you provided in the screenshot, I have checked and this is the section to show the products list of the categories.
I see that the HDMI & DISPLAY PORTS do not the products. I have some solutions to help you resolve this issue.
1/ I have created the ‎/templates/ja_megastore/html/com_virtuemart/category/default-2.php file for the categories layout, you can select this layout here:
I have hidden the product list and moved the title into before sub-categories.
2/ If you want to show the product list, you can add the Title or some description here:
And open the templates/ja_megastore/html/com_virtuemart/category/default.php
line 24 to remove this code:
<h1><?php echo vmText::_($this->category->category_name); ?></h1>