Adding widget IDs to a theme that doesn’t have them

I’ve implemented the Centita theme on this site.

How can I assign an ID to the individual widgets’s sidebox-top and sidebox? The problem is that on that page, I wanted to hide the top widget so I put #cforms-3 {display:none;} into the CSS which did hide the middle part of the widget, but it left the sidebox and sidebox top because there’s no ID i can attribute to those.

These are the two files that I’m assuming drive the widget code…
themewidgets.php: https://pastebin.com/32xWBiJy
sidebar.php: https://pastebin.com/eTk25UFz

…but I don’t know what to do to them to assign an ID to each widget area.

Please advise. Thanks in advance.