HTML, CSS and watching tutorials on how to style the page

As a beginner, I struggled knowing the most appropriate tags to use exactly to make my code look cleaner and readable. Took me a long while. I also struggled being able to attach some of the css elements.

I will want to know how developers are able to bring certain ideas in life using HTML. e.g. with Figma, I could have easily drawn the rectangles and put the bar code image on it. Would have been easier to make the corners of the box curved. I struggled figuring out what to do to generate that box and how to style it. What is the trick?