I don't know where to write down all the info about the padding, font-size and stuff like that on the code screen. I can't see what I'm doing wrong.
I don't see any errors, it even says at the top left that you finished the code. What's the problem?
You have to put all of that CSS code in your main.css file.
To keep things tidy, HTML code goes in index.html and CSS code goes in main.css.
This explains things in more detail: