Having trouble creating a responsive design (can't find parent classes or IDs)


Hello my blog is called Quartzfeather (I can’t add links but if you search it should be the first one to come up) and I’m trying to create a responsive design. I’m currently struggling with making my post section, sidebar, and footer full width because I can’t find the correct parent classes or IDs. I’ve tried my blogger tricks’ post on how to find them but I still can’t find them. Can someone help me?