Direct Linking google with my webpage

Hi,

using a custom theme. and I’m trying to work out how to get this working.

“Link your website
By adding a short line of code to https://www.sitename.com, you can make your Google+ page eligible to show up on the right-hand side of the Google search page for relevant queries and make your Google+ page more discoverable. Learn more
Ask your site’s webmaster to add the following line of code to your site’s homepage:
Google+
You can also email these instructions to your webmaster
Check that the line of code has been added to your site’s homepage and that the modified homepage is live on your site. Then try testing again.”

I’ve put it in header.php (just about the </head> and its not verifying on my google+ page. Help needed. I’ve modified the header.php in which is located in the folder when the theme sits.