Inserting image into post content – Front End

The content of the post is just that – the value of post_content field. You could retrieve HTML for attachment by wp_get_attachment_image() and either pass it to wp_insert_post() initially (will need to create attachment earlier for that) or use wp_update_post() to assign content to already existing post.

Set featured link not showing

your theme needs to support Post Thumbnails to have the featured image meta box… Add this to your functions.php file: add_theme_support( ‘post-thumbnails’ ); See http://codex.wordpress.org/Function_Reference/add_theme_support#Post_Thumbnails