// Process the edit form
 add_action('wp_ajax_process_edit_form', 'process_edit_form');
 function process_edit_form() {

    require_once(ABSPATH . "wp-admin" . '/includes/image.php');
    require_once(ABSPATH . "wp-admin" . '/includes/file.php');
    require_once(ABSPATH . "wp-admin" . '/includes/media.php');

    $image_file = $_POST['imageFile'];
    $image_file_name = $_POST['imageFileName'];

    $post_to_edit = get_post($_POST['postId']);

    // Set Image File
    if ($image_file["size"] > 0) {
        $cover_art_id = media_handle_sideload( $album_cover, $pid );
        wp_set_object_terms( $cover_art_id, 'cover_art', 'category');
        update_post_meta($pid,'music_art',$cover_art_id);
    }


 }

<form enctype="multipart/form-data">
  <input type="file" name="image_file" id="image_file" />
  <input type="submit" value="Save Changes" tabindex="6" id="submit" name="submit" data-id="<?php echo $post->ID; ?>" />
</form>

$(document).on("click","#submit", function(e) {
    e.preventDefault();
    $this = $(this);
    postId = $this.data("id");
    imageFile = $this.closest("form").find("#image_file").val();
    if (imageFile != "") {
      imageFileName = $this.closest("form").find("#image_file").val().split('\').pop();
    } else {
      imageFileName = "none";
            };
   data = {
      action: 'process_edit_form',
      postId : postId,
      imageFile : imageFile,
      imageFileName : imageFileName
   };
   $.post(ajaxurl, data, function (response) {
   });
});

$ajaxurl = "<?php echo admin_url('admin-ajax.php');? >";

var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";
                var formData = new FormData();

                formData.append('$Parent_Post_ID', $Parent_Post_ID;
                formData.append('$thevideo', $thevideo);
                formData.append('action', 'watermark'); // action should be the name of the function you want to call in your functions.php

                $.ajax({
                    url: ajaxurl,
                    type: 'POST',
                    data:formData,
                    cache: false,
                    //async: false,
                    processData: false, // Don't process the files
                    contentType: false, // Set content type to false as jQuery will tell the server its a query string request
                    success:function(data) {
                        //alert(data);
                        //data can consist of anything you want to retrieve from the process

                        var datarray = data.split(',');

                        $attach_id = datarray[0];
                        $whatever = datarray[1];
                        $whatever = datarray[2];


                        alert('All Done :)');

                    } // END Ajax Success

                }); // END Ajax Request

$attach_id = media_handle_upload($file_handler,$Parent_Post_ID );