CSS basics

first to style a element you want in html you need to chose if you will use option 1 or option 2, this is option number one
Add the <style> elemant under the code you want to style. Option 2:
create a new file called "style.css" inside it start your code. Inside your "style.css" file, you can start by selecting an HTML element and giving it style.
For example, to change the background color of the whole page, write:
body {
  background-color: lightblue;
}

To style a heading like <h1>, you can write:
h1 {
  color: darkgreen;
  font-family: Arial, sans-serif;
  text-align: center;
}

To style a paragraph, use:
p {
  font-size: 18px;
  color: black;
}

You can also give your own class name to any element and style it like this:
.my-box {
  border: 2px solid red;
  padding: 10px;
  background-color: yellow;
}