Concrete5 has a simple way to add Google Analytics code to your website.

• Login to your dashboard
• Click on Settings to access the sitewide settings menu.
• Paste your Google Analytics tracking code into the provided space "Tracking Code" and click save.

If you are desiging your own theme, you will need to add the following to your theme's footer just before the tag;

Loader::element('footer_required'); 

You should then be able to follow the steps outlined above.