Changing column width in Dataset

I am trying to figure out how to change the column widths in the dataset widget. It seems like it defaults to equal width for the columns, but I need one to be about 75% and one to be 25%. Is that possible? I keep seeing references to using CSS to alter it, but I can’t find where to use that. I am using the cloud server.

You can edit the CSS to do that.
td:nth-child(1){ /* first child = first column*/
text-align: left;
padding-left: 80px;
width: 2840px; /*This is where you can put a static value of the width size. */

Where do I edit the CSS? I don’t see that as an option in the cloud CMS.