You may need to clarify a little more about what you are asking… but I’ll think I can answer your question.
If you need to get to the style sheet that already has the CSS code written then you want to go to Appearance > Editor then scroll down to the bottom of the page where you’ll find style.css on the right hand side.
If you are asking about where you can add custom CSS to your site. You can actually add it to the style.css file; however, I would recommend going to Appearance > Theme Options where you’ll find an option at the bottom left for Custom CSS.
Hope this helps but let me know if you need anything else.
Cheers
Buck
