Hi,
It's not in Display>Views.
As I said, it's in the HikaShop configuration page.
So go in the menu Components>HikaShop>Configuration of your backend.
There, click on the Display tab. And under the "CSS" section, you'll see the CSS options where you can edit them to add your own CSS as explained in the link I gave you :
www.hikashop.com/support/documentation/1...ize-the-display.html
Please look there. There is even a screenshot (albeit a bit old) which displays the HikaShop menu, the configuration page, the display tab and the CSS options:
www.hikashop.com/images/stories/doc_display_3.png
Note that this doesn't require any HikaShop knowledge. You could add that CSS code I gave in the main CSS file of your Joomla template (or any other CSS file loaded on the page) and it would work as well as if you add it in HIkaShop.