Add the code provided by Google to the relevant template file in your current theme. So, in short, it depends upon where you want it to appear on your site.
i am using classic theme of word press and want to add google search box at the header of the blog?
then where i want to add the codes provided by the google?
Thanxs
Read this post to add Ajax-powered Google CSE with in few mintues on your site.
dude..
go to this website:http://www.googleadsensecode.com/..
get the code you want
now 1st decide where do u want to place google ads on the header e.g left or right etc,
Then go in header.php & find the closest postion to the palce where you want the google ads to appear, if you can’t find the place just paster the code, refresh the page to see the result
& do this by just make a new div like this & put the code inside it:
<div id="g-search">
<!-- Start Here -->
<script type="text/javascript"><!--
google_ad_client = "pub-2151667935419035";
/* 120x600, created 7/17/08 */
google_ad_slot = "8233032726";
google_ad_width = 120;
google_ad_height = 600;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
<!-- End Here -->
</div>
then adjust the exact position by using CSS styling e.g margin & padding etc
