[Plugin: Page Meta] Installation help

Hello!
I am very new to WorldPress and php I am trying to install Page Meta plugin. I am not able to follow this instruction on #3:

"Replace <?php wp_title(); ?> with <?php if (function_exists('meta_title')) { meta_title(); } else { wp_title(); } ?> in your header template, this can be found within the tag."

Here is <title> </title> code from my header template:

<title><?php if (is_home()) {
	echo bloginfo('name');
} elseif (is_404()) {
	echo '404 Not Found';
} elseif (is_category()) {
	echo 'Category:'; wp_title('');
} elseif (is_search()) {
	echo 'Search Results';
} elseif ( is_day() || is_month() || is_year() ) {
	echo 'Archives:'; wp_title('');
} else {
	echo bloginfo('name'); echo wp_title('');
}
?></title>

Kindly tell me where do I need to make changes.
One more question:
How do I add <meta name=’description’ to my home page?

http://wordpress.org/extend/plugins/pagemeta/