download and add jquery to a site code example

Example 1: how to download jquery

You have quite a few options

You can get the whole source
Uncompressed dev: https://code.jquery.com/jquery-3.4.1.js
Compressed production: https://code.jquery.com/jquery-3.4.1.min.js
You the simply save the code into a Javascript file and include it in the usual way
<script type="text/javascript" src="jquery.js"></script>

Or point to a CDN, such as Google's
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>

You can get it using NPM, Yarn or Bower
npm install jquery
yarn add jquery
bower install jquery

You can even get the latest builds from GitHub
git clone git://github.com/jquery/jquery.git

Example 2: how to use jQuery

<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>jQuery</title>
  </head>
  <body>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
    <script>
      //jQuery code
    </script>
  </body>
</html>