1. Log in to your dashboard--> layout- -> Edit HTML

2. Click on "Expand Widget Templates"

3. Search "Ctrl+F" and find </head>.

4. Before </head> add next code: 

<script type="text/javascript" src="http://descarca.googlecode.com/files/jquery.js"></script>

<script type="text/javascript">
$(document).ready(function(){

 $(".btn-slide").click(function(){
  $("#panel").slideToggle("slow");
  $(this).toggleClass("active"); return false;
 });
 
  
});
</script>

If you have Jquery already installed on your template delete the red line.
5. Search for ]]></b:skin> and before it paste the next code:

#panel {
 background: #fff;
 width: auto;
 height: 200px;
 font: 90%/120% Arial, Helvetica, sans-serif;
 color: #000;
 padding: 10px;
 text-align: justify;
 display: none;
}
.slide {
 margin: 0;
 padding: 0;
 border-top: solid 4px #000;
 background: url('http://img406.imageshack.us/img406/6227/btnslide.gif') no-repeat center top;
}
.btn-slide {
 background: url('http://img535.imageshack.us/img535/2351/whitearrow.gif') no-repeat right -50px;
 text-align: center;
 width: 144px;
 height: 31px;
 padding: 10px 10px 0 0;
 margin: 0 auto;
 display: block;
 font: bold 120%/100% Arial, Helvetica, sans-serif;
 color: #fff;
 text-decoration: none;
}
.active {
 background-position: right 12px;
}

You can change the widht height, padding etc. values according to your needs.

6. Now go to Layout-->Page Element and click on "Add a gadget". Select "html/java script" and add the code given below and click save.

<div id="panel">
 <!-- you can put content here -->
</div>

<p class="slide"><a href="#" class="btn-slide">Slide Panel</a></p>


DEMO:

demo demo demo demo demo demo
demo demo demo demo demo demo
demo demo demo demo demo demo