Google Analytics is an indispensable (and free) tool for any business with a website. It allows you to see how many people are viewing your website, where they are coming from, what pages they are looking at, how long they stay on your site and a vast array of other highly valuable information. In order to take advantage of this amazing tool, you must add it to your site as soon as possible, because Google Analytics can only track data from the point you add it to your site and you are loosing valuable data every day the tracking code is not installed. Google Analytics is also a core requirement for using any Smart Links you create.
Setup Google Analytics Yourself
To help you get started, Google provides a great checklist and guide for using Google Analytics
Google Analytics Setup Checklist