How do I get rid of the BORDERS around all my images?

I don’t know why this is SO difficult to do such a simple task! WordPress extremely unintuitive. I’ve tried MANY different things trying to get rid of the annoying border around images.

I don’t know why the default “style.css” file has no code in it. All it has is a comment… I’ve searched EVERY php file in the editor and can’t even find the word “img”. How the fuck am I supposed to change the posted image attributes when the word “img” doesn’t even exist?

I searched “image.php” and I CANNOT figure it out.

I’ve tried editing style.css to display images without borders but it doesn’t work. I’ve tried going into the text section of the post and manually adding no border to the HTML but it doesn’t work.

PLEASE HELP!!!!!!!!!!!!!!