adding code to theme

HI

I am using the WPMU modified "Spirit theme".

I need to add Paypal marketing solutions script to the website.

<!– PayPal BEGIN –>

<script>

;(function(a,t,o,m,s){a[m]=a[m]||[];a[m].push({t:new Date().getTime(),event:'snippetRun'});var f=t.getElementsByTagName(o)[0],e=t.createElement(o),d=m!=='paypalDDL'?'&m='+m:'';e.async=!0;e.src='https://www.paypal.com/tagmanager/pptm.js?id='+s+d;f.parentNode.insertBefore(e,f);})(window,document,'script','paypalDDL','22f8b5cf-169d-45e1-ac74-34a3a20dd943':wink:;

</script>

<!– PayPal END –>

The instructions are:

Scroll down to the bottom of the footer.php file. Paste the PayPal script before the ending body tag. NOTE: Script placement may vary depending on the WooCommerce theme used.

Follow these steps for every page in your website where you want to collect information on your visitors. Note that some sites use a method that stores the tag and automatically copies it to all of your pages, so you won't need to add it manually to the HTML file for each page.

How do I do this please.