[SOLVED] Add Adsense section targeting code to single.php

Another thread on the forum mentioned adding the code immediately below to the index.php as there is no single.php

<?php if ( is_single() ) { ?>
YOUR CODE HERE
<?php } ?>

The code I need to add is

<!-- google_ad_section_start -->

<!-- google_ad_section_end -->

In the middle of Google's 2 lines of code I also need to have the code that relates to the entire content of each post. I am new to coding and know it should look something like the_content() but not sure exactly.

Can you tell me what code in its entirety I need to add to index.php and where exactly I should put it?

Thanks very much.