Need to add windows and doors on complex surface

I have this drawing that I downloaded off the 3D warehouse of a shipping container. I want to add some windows and doors, but I can’t seem to figure out how to get it to cut in on the ribbed siding.

Commercial_Shipping Container_40’.skp (40.9 KB)

Sounds familiar. Take a look at this thread: Cutting a hole in a shipping container


Ok, I’m not getting where your box came from. I think I understand everything else.

It’s a basic Sketchup Shape, make it with the rectangle and push/pull and delete one or two faces.
Introducing Drawing Basics and Concepts