In order to create a marker you need to do the following:
Demo forked from your example: http://jsfiddle.net/lucuma/xUUxn/852/
JS:
var marker = new google.maps.Marker({
position: new google.maps.LatLng( -12.043333,-77.028333),
map: map,
title: 'Hello World!'
});
To add an info window overlay:
var contentString = '<div id="content"><h1>Overlay</h1></div>';
var infowindow = new google.maps.InfoWindow({
content: contentString
});
google.maps.event.addListener(marker, 'click', function() {
infowindow.open(map,marker);
});