This is the jet pack CSS, and I added the code at the end of the comment, but it doesn't seem to work. Did I do it right or might have missed something.
Welcome to Custom CSS!
CSS (Cascading Style Sheets) is a kind of code that tells the browser how
to render a web page. You may delete these comments and get started with
By default, your stylesheet will be loaded after the theme stylesheets,
which means that your rules can take precedence and override the theme CSS
rules. Just write here what you want to change, you don't need to copy all
your theme's stylesheet content.