Here is a good link explaining how to add Google Analytics to your WordPress website.

We are fans of Plugins for WordPress.
That said we try to limit the amount of PlugIns on a WordPress Websites. It is the right way to do web development.  If you don’t know what you are doing, or have a pro web developer, you can install the tracking code.

PRO TIP: Always add changes to the core files in the CHILD THEME and not the main Theme core files. You could break the website. 

If you don’t what I am talking about, DM me and we can help out!