Theme Error

Replies: 2

After I activated the Plugin, I got this error

Error : Please fix your theme to make plugins work correctly. Go to the Theme Editor and insert the following string: <?php wp_head(); ?> Please enter it just before the following line of your header.php file: </head> Go to your theme editor.

I couldn’t find header.php instead i found wp-blog-header.php. on Opening the file, this was inside:
?php
/**
* Loads the WordPress environment and template.
*
* @package WordPress
*/

if ( !isset($wp_did_header) ) {

$wp_did_header = true;

require_once( dirname(__FILE__) . ‘/wp-load.php’ );

wp();

require_once( ABSPATH . WPINC . ‘/template-loader.php’ );

}

So What should i do now? Where to paste the code and get the plugin activated on my account.