How to change width of the category element in the Constructor theme?

I’m using the constructor theme and I want to decrease the width of the category element relative to my background photo. I want the pages on my blog to show the posts within the opaque category element while the edges of the background photo shows around the sides. You can see an example at http://www.bayoubonvivants.com. Also, is there a way to modify the width of the sidebar as well? Any help is greatly appreciated, thank you!