In order to target specific elements on a page with CSS, you will have to figure out which HTML tags/classes to use. This can be easily done on your browser using the built-in development tools.
- Right click on the element you wish to style with CSS
- Click 'Inspect' (Google Chrome) or 'Inspect Element' (Firefox, Internet Explorer, Safari)
You will now see the HTML that makes up the webpage, focused on the line(s) related to the element you're targeting. In addition, Inspect Element allows you to temporarily edit the HTML or CSS of a page which will go away once the page is reloaded.