Can't get my CSS code to show up with the HTML when I open a preview

How do I make my CSS code affect my HTML code? I would really appreciate the help, thank you.

@Geo

In your HTML code, place your CSS external anchor tag code immediately before the closing head tag. I do hope this helps. If you have further confusion, you can let everyone know whether you are talking about internal CSS or Inline CSS. Warm Regards.

Yep, that worked. Thank you so much!