single – Edit the publication template on the theme Divi

I'm using the Divi theme on my site and I want to add code on the release template. I know I'm supposed to edit the single.php file, but everything I do about the file does not work. I even tried to leave the file empty, then leave it almost empty except for a little "

"or something, but nothing happens.

I've tried to do the same thing on the file nineteen and nothing happens there either.

Am I missing a step or something?