Wordpress: Customize Admin Dashboard

custom-wp-dashboard.php

<?php
//Add a custom admin dashboard welcome widget
function custom_dashboard_widget() {
	echo '<h1>Welcome to your new WordPress site built by an awesome developer</h1>';
}
function add_custom_dashboard_widget() {
	wp_add_dashboard_widget('custom_dashboard_widget', 'Integrity Welcomes You To WordPress!', 'custom_dashboard_widget');
}
add_action('wp_dashboard_setup', 'add_custom_dashboard_widget');

//Set default dashboard columns to 1
function so_screen_layout_columns( $columns ) {
    $columns['dashboard'] = 1;
    return $columns;
}
add_filter( 'screen_layout_columns', 'so_screen_layout_columns' );
function so_screen_layout_dashboard() {
    return 1;
}
add_filter( 'get_user_option_screen_layout_dashboard', 'so_screen_layout_dashboard' );

//Remove unneeded admin dashboard widgets
function disable_default_dashboard_widgets() {
	remove_meta_box('dashboard_right_now', 'dashboard', 'core');
	remove_meta_box('dashboard_recent_comments', 'dashboard', 'core');
	remove_meta_box('dashboard_incoming_links', 'dashboard', 'core');
	remove_meta_box('dashboard_plugins', 'dashboard', 'core');
	remove_meta_box('dashboard_quick_press', 'dashboard', 'core');
	remove_meta_box('dashboard_recent_drafts', 'dashboard', 'core');
	remove_meta_box('dashboard_primary', 'dashboard', 'core');
	remove_meta_box('dashboard_secondary', 'dashboard', 'core');
}
add_action('admin_menu', 'disable_default_dashboard_widgets');
?>

I'm using onetone theme .. how can I let the editor role user to use slider from onetone options and add the images he want??