Make resume form responsive

I’m trying to make the form where the resume is submitted responsive. I’ve been able to edit the form.php file to arrange some things. However, I can’t figure out how to get the wp_editor area to fit within a mobile device window. I don’t know enough about PHP to be able to add a CSS class to the editor, so I’m kind of stuck. Right now the editor area is the only part of the form that won’t resize itself. The location of the form is:

https://parkwayschool.com/beta/apply/

If anyone could point me in the right direction, I’d greatly appreciate it.

https://www.ads-software.com/plugins/resume-submissions-job-postings/