As you may have heard, Google is discontinuing Urchin, therefore the Urchin analytics service for Cloud Sites will be phased out.  A popular alternative is the FREE Google Analytics™ web analytics service.  Here is a step-by-step walkthrough on how to sign up for this service.

• First, go to the Google Analytics™ site to get started.  Sign in using your existing Google account, or create a new account if you do not already have one.

• Click on the Sign Up button where it says 'Start using Google Analytics'.

• Enter the Account Name that you would like to use for your website.  When entering your website URL you will have the option for monitoring an http site or a secure https site.  Enter your local time zone, and choose your Data Sharing preferences. You can change these at a later time, if you wish.

• Accept the User Agreement and click Create Account.

• When your account is created, you will be provided with a code snippet allowing Google Analytics to track data from your site.  Copy and paste the tracking code to the pages you wish to track.

• Give Google Analytics™ web analytics service approximately 12-24 hours to begin reporting traffic analytics data for your website.

Additional Resources 

Google Analytics Documentation

Wordpress plugins for Google Analytics:

Google Analytics for WordPress

Google Analyticator

Google Analytics Modules:

Joomla!

Drupal