To install the script, unzip and upload the files to somewhere, say http://localhost.
Login with your Blogger account. Then edit your template like this:

1. Add a link to the JavaScript file inside <head> and </head>, e.g.:
   <script type="text/javascript" src="http://localhost/bloglendar.js"></script>

   You can also copy and paste the code into the template directly by enclosing it inside:
   <script type="text/javascript"> and </script>

2. Add a link to the CSS file inside <head> and </head>, e.g.:
   <link rel="stylesheet" type="text/css" href="http://localhost/bloglendar.css" />

   Again, you can also copy and paste the code inside:
   <style type="text/css"> and </style>

3. Add an onLoad event to your <body> element:
   <body onload="drawCalendar()">

4. Replace <BlogDateHeader> to </BlogDateHeader> with this code:
   <BlogDateHeader>
      <script type="text/javascript">
         var postDate = "<$BlogDateHeaderDate$>";
         realDate = datesplitter( postDate,dateType );
         anchorDate = realDate.valueOf();
         <!-- modified [Andy 1-Sep-2003] -->
         if ( currentMonth == null )
            currentMonth = realDate.getMonth();
         if ( firstPostDate == null )
            firstPostDate = realDate;
         if ( realDate.getMonth() == currentMonth )
            links[realDate.getDate()] = "#d" + anchorDate;
         document.write("<a id='d" + anchorDate + "'></a>");
      </script>
      <$BlogDateHeaderDate$>
   </BlogDateHeader>

   You may like to add the heading like <h1>, <h2> back into this code.

5. Finally add this code to where you want the bloglendar to appear:
   <span id="bloglendarHere"><!-- tells the script where to put the bloglendar --></span>

Done! You may like to edit the CSS to make it more suitable for your special blog! ^__^