Where to ADD the code?

The code needs to be added to your website's HEADER.

This is very easy to do if you are using Wordpress.

Step 1: 

Goto Plugins and click ADD NEW

Step2: 

Search for "Header Footer Code Manage" by 99 Robots

Step3: 

Download and Activate Plugin

Step4: 

On the left column, click the new tab that says HFCM

Step5:

Click ADD NEW SNIPPET

Step6: 

Paste in the code into the Snippet / Code box, and give it a name

Step7: 

 Click SAVE

Bonus Step: Clear Website Cache