This tutorial will guide you that how to add Google analytics tracking code in your PrestaShop 1.5.x.
1. First of all go to the back-end and get login
2. Go to the admin section, and then Modules, and then Modules menu:
3. Search for the Google analytics module
4. Install the module
5. Click the configure link in order to configure and set up this PrestaShop Google analytics module
6. Then you have to specify the username ID of the Google analytics. For better understanding of how to create your Google analytics id go to this official link here: http://www.google.com/analytics/index.html and then save changes.