Browse to www.google.com/analytics and sign in with your Google Account.
You will need to enter the URL (web address) of the site you want to track. Google will provide you with some custom code that must be copied and pasted into your website. This code snip it is accessed each time someone views the page content and reports the findings back to Google. Once you or your website designer has placed this code on the site, sit back and watch the data start to come in. After a few weeks you will have very useful information about how people are using your website and where you can improve content or flow to better improve usability.

