Classifieds - "override this file in your active theme"?

I've been trying to get the Classifieds plugin to look like my theme, but I'm not exactly sure how to. When I go into the Plugins settings, there are no theme-related options, so I presumed it inherited the look of the active theme and placed the content in the appropriately designated area where everything else goes.

Having looked through the plugin's directory, I see that the plugin is using files under the /plugins/classifieds/ui-front/general directory which contains various PHP files controlling the look of it. When I open them up and look at the top of the file, I'm greeted with...

* The template for displaying the Checkout page.
* You can override this file in your active theme.

My problem is - how do I override that file in my active theme? I thought I could edit them in the same directory, but I know when the plugin gets updated then the files and changes I would make will be overwritten. I've tried duplicating the files into my themes folder with no luck.

So I'd say I'm clearly missing something here and if anyone could help me figure it out, I'd really appreciate it. Thanks!