How to link your post title to external links

First open your functions.php file and add this code to it.

function print_post_title() {
global $post;
$thePostID = $post->ID;
$post_id = get_post($thePostID);
$title = $post_id->post_title;
$perm = get_permalink($post_id);
$post_keys = array(); $post_val = array();
$post_keys = get_post_custom_keys($thePostID);
if (!empty($post_keys)) {
foreach ($post_keys as $pkey) {
if ($pkey=='url1' || $pkey=='title_url' || $pkey=='url_title') {
$post_val = get_post_custom_values($pkey);
}
}
if (empty($post_val)) {
$link = $perm;
} else {
$link = $post_val[0];
}
} else {
$link = $perm;
}
echo '<h2><a href="'.$link.'" rel="bookmark" title="'.$title.'">'.$title.'</a></h2>';
}

These code must be placed in php tags

Now open your index.php file and find this code

<h2><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h2>

Finally replace it with this code

<?php print_post_title(); ?>

Done