Absent any specifics in your question, it seems to me that what you want to fix/change is either the CSS used, or the template used to build the page.
If you are trying to change the CSS styling of a particular area (called ‘elements’), then use the developer tools (like Firebug on Firefox; or the native developer tools in FF or Chrome), to inspect the element’s CSS. Use the CSS name as shown in the CSS inspector pane in your child theme’s style.css file to change the ‘look’ of that element (like background color, margins, padding, etc).
If you are trying to change what WP ‘builds’ on the page (the generated page source), then you need to dig into the templates that the theme uses by copying a template to your child theme folder, then editing that file.
There are some great tutorials out there for either purpose. Start at a site like www.wpbeginner.com for a tutorial that will help.
More specific questions will get you a more specific answer.