? Boxing help my "Our Courses list"

dear all,

finally! I passed all test Product landing page project3 at the FCC :sunny:

But I am not happy with some part I couldn’t manage to put “our courses” list in a box on the page.
this is my link from codepen-io :

I checked and worked w3school materials as well …where could I learn this specific part.

many many thanks all your time