To use Google WebMaster Tools you have to confirm to be the owner of the site.
There are different ways to do this action, one of them is to add a meta tag named 'google-site-verification' at least into head of the main page of the site. See "https://support.google.com/webmasters/answer/35179" for details.

This hook makes two things:
* add a field inside analytics section of site settings to allow site admin to set verification code
* add the meta tag to all pages of the site