I recommend Ultimate GA plugin. Easy to set up. Just copy the ID from the code Google Analytics generates for your site, paste in and you are set. Way better that manually editing php files. If you change the theme you had to do again. Not so with the plugin.
Ultimate GA settings page
What is nice about this plugin is the extra features you can enable:
- ignore login in user greater than a user level of 8 will ignore visits by Administrator, a good idea not to skew the data by your visits posting and developing site.
- enable tracking links for external links
- enable tracking links for downloads
