Editing the CSS to enlarge and center site title

Hello! I've spent the last 3 hours trying to figure out how to enlarge the font size and center the site title. Please Help! I was able to preview the edit through the inspect element but can't replicate the action in the theme code. The additional css feature in word press does absolutely nothing for me either. And nothing I've tried will move the site title to the center. I've tried clearing the various catches and disabling my plugin "use any font". Any ideas what else I can do? I don't have any experience with CSS and have googled everything I've tried. :) So any instructions given-- the more detailed the better. Thanks in advance!