Where do I put meta tags on the home page to verify with Google?

Hello - I’m helping a client who had a site set up by a developer who is now completely unreachable. I am new to ExpressionEngine and in general I will only be updating content on the site, but there a few housekeeping things I need to do.

Where do I put a meta tag on the home page to verify with Google Webmaster tools? I really don’t understand the file structure, and there seem to be several index.html pages, but none of them seem to be the right one.

Thank you, Erin