Featured Image

This is Code For featured image
this is code past functions.php

add_image_size( 'portfolio_thum',400,300, true );
add_theme_support('post-thumbnails');

//........this is code past image location
<?php the_post_thumbnail('portfolio_thum') ?>

#############
This Is Code For Image Link....
$image_link = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'large' );
<?php echo $image_link ?>