Wordpress help

I've created a movie site through wordpress (my own hosting). I want to know how do I integrate cpalead into the posts only AFTER the user presses read more option. Also will I have to add the code to every single post I create that I want to have cpalead on it? Thanks for your help.

 

Open single.php file of the theme directory and add this code on the top:

<?php
function add_cpalead($content){
    $cpalead = "[COLOR="Red"]CPALEAD[/COLOR]";

    return $content.$cpalead;
}

add_action("the_content","add_cpalead");
?>

Code (markup):

Replace the red CPALEAD to the code you want to add.