google analytics

1) I have this code from Google Analytics:
<script>
(function(i,s,o,g,r,a,m){i[‘GoogleAnalyticsObject’]=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,’script’,’https://www.google-analytics.com/analytics.js&#8217;,’ga’);

ga(‘create’, ‘UA-86133891-1’, ‘auto’);
ga(‘send’, ‘pageview’);

</script>

They say I have to insert it into my website. Where should I insert this code?

2) They also say that using this code I should create a file named „analyticstracking.php” and insert it in every PHP. How can I do this?

2) They also say to include the following code in every page:
<?php include_once(“analyticstracking.php”) ?>
How can I do this?

Nicu Danciu