Custom Page styling/settings

Hi, I’m not fond of the settings that override my theme for the Courses page, but I assume I might like to know how to change this on any other custom page as well as I continue working on the site.

None of my theme settings take any effect, and the page is boxed and uses the default post archive which has a sidebar I don’t want.

I’m probably missing something simple but can you explain how to set this?