how to add custom fonts to google sites code example

Example 1: add google font

CSS
@import url(https://fonts.googleapis.com/css?family=Roboto);

HTML
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto"/>

body{
  font-family: "Roboto";
}

Example 2: use google fonts in css

@import url('https://fonts.googleapis.com/css?family=Open+Sans&display=swap');