You try to enter the theme editor, continue to enter into header.php.baru paste adsense code in accordance with both size and color theme .. good luck..!?!..
and do you know of a plugin that will do what he wants? You probably don't know what he wants you just wanted to get a post. There is no need for a plugin and there probably isn't one that will only let him show the ads in the header on certain pages only (which is what he wants). -- I wish people would stop saying "use a plugin" just so they can get a post on their post count. There has been many say it already and he don't need a plugin.