Child Theme and plugin question

I have a created a child theme, so far so good.

And I know that I just need to duplicated the files and folder structure of the parent theme folder. But what if I want to make changes to .php, .css, .mo. .po files that that are outside the parent theme folder? Like the prettyPhoto plugin or some VC stuff. \wp-content\plugins\js_composer\

What do I do then?

Thanks