How to add left and right margins in Topic?

Hi

I am using RH10, as part of TCS4. I am creating screen layouts by just modifying the existing ones.

I noticed that there is no margin/ space between the topic border and the topic content in it. When I searched for that in mobile.css, I did not find any relevant reference. When I did a Inspect Element on Firefox, it pointed to default.css which I don't find in my Project Setup pod.

How can I modify it? Here is the screenshot of the issue I am referring to:

Please advise.

Sreekanth