The easiest way to use Google Analytics with your Dartmouth site is as follows.
First go to the Plugins item on the menu, and Activate the "Google Analyticator" plugin.
Once active, you should see a new Google Analytics item in the menu on the left.
Click on the Google Analytics menu item and select Google Analytics again.
You should see the following screen:
Click the "Continue Without Authentication" button.
On the next screen, change Disabled to Enabled, and enter your Google Analytics tracking code, which should look something like UA-12345678-1.