Advice needed for editing the published css files

Hi, I am trying to edit the css in the published files and understand the issues relating to this practice. However there are a few specific requests that I am trying to solve. For example I cannot seem to identify the border space around the 360 content file (image attached) I would like to remove the left and right space.

I understand that the class / div names will possibly change with software updates but if I can get a better understanding of how to identify the relevant elements/css etc than that would help me. I've looked around the community and online but not a lot of resources available. If anyone has any experience/advise on editing the css player properties then that would be really appreciated.

Many thanks