<?php
function plugin_add_settings_link( $links ) {
    $settings_link = '<a href="options-general.php?page=plugin_name">' . __( 'Settings' ) . '</a>';
    array_push( $links, $settings_link );
  	return $links;
}
$plugin = plugin_basename( __FILE__ );
add_filter( "plugin_action_links_$plugin", 'plugin_add_settings_link' );
?>