Create plugin admin with external code

Create plugin admin with external code

I try use script create external wordpress and manage from admin of wordpress , for this i create this plugin :
<?php
/*
Plugin Name: Search TLDs
Plugin URI: www.myweb.com
Description: Add Domains
*/
if (is_admin())
{
?>
<?php
function domi()
{
locate_template( array( 'modulos/test.php' ), true, true );
}
add_action('after_setup_theme', 'domi' );
}
?>
The problem the content no show right into the admin and other problem all time tell me this :
Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at .....
How i can include right the content of my script into my admin and no give this alerts into wordpress , because my script works out wordpress but i want insert for manage into administration
Thank´s , Regards !