First you need visit http://www.google.com/analytics/ to get the javascript code. Then paste the code in page_index.html of your html template. It is not need to put the code in every html templates, because file page_index.html is used as main template for another template files.
Take attention in pasting the javascript code, you need to put {literal} before the code and {/literal} at the end. This is needed to avoid error with the smarty template system.
Example:
{literal}
... Javascript Blocks here...
{/literal}
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