How to link CSS to HTML & CSS animation basic

It's very simple to link CSS with HTML.You just follow two steps.

Step 1: Create a CSS file which name (style.css) is already been in the ref link!
Step 2:Then Link it following....  <link rel="stylesheet" type="text/css" href="style.css">

 Animation:
h1
{
  animation-duration: 6s;
  animation-name: slidein1;
}
@keyframes slidein1 {
  from {
    margin-left: 100%;
    width: 300%;
  }

  to {
    margin-left: 0%;
    width: 100%;
  }

}