1st of all, make sure you have compiled the course with sourcemaps enabled. If you're doing it by hand, run `grunt dev` or in the authoring tool, turn on source maps in the project settings.

Once you have done that, reload the course in the preview or browser.

Then open up the web inspector and select the element you want to inspect:

On the right you'll see all of the file names where the applied styling lives. Find the style and file lines that are wrong and edit the styles in the browser to check. Then go make the edits in the course files or authoring tool.

It sounds like you need to learn how to use the web inspector and possible learn about style precedence? If so, there are many courses and explainers online.