Aperio and header spacing

I inherited the maintenance chores of a website using the Aperio theme, but just discovered that the theme author, bradweb, does not provide any support. Can anyone help me with the following:

I created a new homepage (published, but not linked to anything: https://www.creativeedgesoftware.com/test-home-page.) It includes a slider created in Slider Revolution. There are huge gaps above and below the slider. I believe the CSS fix would be something like: .page-id-1975 .header-margin{margin-top: 0;} and .page-id-1975 .content-box{padding: 0 30px;} — but the theme and slider environment are new to me, and I’m unsure where to add the CSS — or if my CSS is correct.

Thanks!