Twenty twelve child theme google verification

I’ve saved twenty twelve to child theme. Added style css. Now I’m trying to add google verification to this. I know this is a function php but I don’t understand where to add it in the css or do I copy a function php and add it to the editor in the child theme? I barely know php so I’m really flying by the seat of my pants.
If I do add it to the css where would I place it. When you look at the css I don’t see a head section. Any help would be appreciated.
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