Can someone help me with a lightbox please!

Can someone help me with a lightbox please!

Hello, I work for a small non-profit and we are looking to add a lightbox to our homepage. I have no web design experience, although I'm in the process of learning HTML/CSS and then will move on to JS.

That said, I can't figure out this lightbox. Right now, I have it where if someone clicks on the linked word, it'll pop up. However, I'm hoping to change two things.

1. I need it to pop up automatically when someone visits the page.
2. I really need to link the image someone else. The way it's set up, I can't do that.

Can someone help me please? I've posted the code below. Thanks!

  1. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
            "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <html>
    <head>

    <title>Untitled</title>
    <script type="text/javascript" src="/javascript/jquery/jquery.js"></script>

    <link rel="stylesheet" type="text/css" href="shadowbox.css">
    <script type="text/javascript" src="shadowbox.js"></script>
    <script type="text/javascript">
    Shadowbox.init({
        handleOversize: "drag",
        modal: true
    });
    </script>

    </head>
    <body>
    <a href="lightbox1.jpg" rel="shadowbox">My Image</a>
    </body>
    </html>