add_filter( 'plugin_action_links_' . plugin_basename(__FILE__), 'add_action_links' );
function add_action_links ( $actions ) {
$mylinks = array(
'<a href="' . admin_url( 'options-general.php?page=myplugin' ) . '">Settings</a>',
);
$actions = array_merge( $actions, $mylinks );
return $actions;
}