[Them:Food Blog Pro] CSS Editor not working-can't style anything

I would love to change the font size of my post. I’m extremely new to website design and would appreciate step-by-step. I understand how to use CSS but I just have no idea how to apply it to my theme.

I am using the “Food Blog Pro” theme. I tried using the Appearance — “EDIT CSS” but no text is here. Therefore I supposed that you just add the commands you want and it will update the theme but after trying simple things like changing the background nothing changed. This is the command that I wrote:
/*
Welcome to Custom CSS!

To learn how this works, see https://wp.me/PEmnE-Bt
*/

.site-contet { background:orange; }

Am I just using the Editor CSS wrong or what? I also tried deleting big chuncks in the “Editor”–>Style.CSS but again nothing changed (I have it backed up to restore it).

Any help on how to style my blog would be greatly appreaciated.