When you sign up for Google AdSense you have to verify your account by adding some code to your site.
After you set up your Google AdSense account you’re given a snippet of code to verify your site, along with some pretty cryptic instructions.
Google says to edit your site files and add something after thetag.
But if you’re using WordPress there’s a much easier — and safer — way to do this.
Go into your WordPress admin dashboard and click Appearance > Widgets.
Find the “Custom HTML” widget on the left and drag it into a widget area on the right. It can go in a Footer widget or, if your theme doesn’t have Footer Widgets, it can go at the bottom of your Primary sidebar.
Then, copy the verification code into that Custom HTML widget.
Save the widget and your verification code will now be added to your site.
After your Google AdSense account has been verified you may see a Google Ad show up where you added the widget. You may remove that widget once your account is verified and insert different AdSense ad units instead.