Wordpress Adding image size

functions.php

<?php

add_image_size( 'custom-size', 220, 180 ); // 220 pixels wide by 180 pixels tall, soft proportional crop mode
add_image_size( 'custom-size', 220, 180, true ); // 220 pixels wide by 180 pixels tall, hard crop mode
add_image_size( 'custom-size', 220, 220, array( 'left', 'top' ) ); // Hard crop left top

/*
For Media Library Images (Admin):
--------------------------------
You can also make your custom sizes selectable from your WordPress admin. 
To do so, you have to use the image_size_names_choose hook to assign them a normal, human-readable name…
*/

add_filter( 'image_size_names_choose', 'my_custom_sizes' );
function my_custom_sizes( $sizes ) {
    return array_merge( $sizes, array(
        'your-custom-size' => __( 'Your Custom Size Name' ),
    ) );
}
?>

Thanks a lot!