Add image to posts

i want to add image for posts from functions.php when the theme is activate
i use this code from wordpress doc:

$filename=get_template_directory()."/n4p/resources/first page descriptions/support.jpg";
$wp_filetype = wp_check_filetype(basename($filename), null );
$wp_upload_dir = wp_upload_dir();
$attachment = array(
    'guid' => $wp_upload_dir['url'] . '/' . basename( $filename ),
    'post_mime_type' => $wp_filetype['type'],
    'post_title' => preg_replace('/\.[^.]+$/', '', basename($filename)),
    'post_content' => '',
    'post_status' => 'inherit'
);
$postIdObj=get_page_by_title( "Support", "", "post" );
$postId=$postIdObj->ID;
/*
wp_insert_attachment( $attachment, $filename, $postId );

$attach_id = wp_insert_attachment( $attachment, $filename, $postId );
require_once(ABSPATH . 'wp-admin/includes/image.php');
$attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
wp_update_attachment_metadata( $attach_id, $attach_data );

[In future please wrap your code using backticks]

the problem is that in the upload directory the image don’t exists.
and when i enter on featured images i see 2 broked images and the url is something like this:

http://localhost/bwp/wp-content/uploads/E:web designbwp/wp-content/themes/bestwordpressthemesforphotographers/n4p/resources/first page descriptions/support.jpg

so..can you help me with this?
thanks!