Ideal payment

I need to install ideal payment in my opencart 1.5.6. can some one help me with it, I didnt understand what to do! I got a script from my bank and they says place it in your shop and that is it.
This is de script.

<!-- CODE_START -->

<script type="text/javascript">
<!-- Begin

var Amount = 123;
var PSPID = "TESTiDEALEASY";
var AM;

if (isNaN(Amount))
{
alert("Amount not a number: " + Amount + " !");
AM = ""
}
else
{
AM = Math.round(parseFloat(Amount)*100);
}

var orderID = "1";
mydate = new Date();
tv = mydate.getYear() % 10;
orderID = orderID + tv;
tv = (mydate.getMonth() * 31) + mydate.getDate();
orderID = orderID + ((tv < 10) ? '0' : '') + ((tv < 100) ? '0' : '') + tv;
tv = (mydate.getHours() * 3600) + (mydate.getMinutes() * 60) + mydate.getSeconds();
orderID = orderID + ((tv < 10) ? '0' : '') + ((tv < 100) ? '0' : '') + ((tv < 1000) ? '0' : '') + ((tv < 10000) ? '0' : '') + tv;
tvplus = Math.round(Math.random() * 9);
// End -->
</script>
<style type="text/css">
label {width: 120px; text-align: left;}
button.iDEALeasy {background-color: #FFFFFF;}
</style>



<form method="post" action="https://internetkassa.abnamro.nl/ncol/p ... andard.asp" id="form1" name="form1">
<script type="text/javascript">
document.write("<input type=\"hidden\" NAME=\"PSPID\" value=\"" + PSPID + "\" />");
document.write("<input type=\"hidden\" NAME=\"orderID\" value=\"" + (orderID + ((tvplus + 1) % 10)) + "\" />");
document.write("<input type=\"hidden\" NAME=\"amount\" value=\"" + AM + "\" />");
</script>

<input type="hidden" name="currency" value="EUR" />
<input type="hidden" name="language" value="NL_NL" />
<input type="hidden" name="PM" value="iDEAL" />
<button class="iDEALeasy" type="submit" name="submit1" value="submit">
Betalen met<br />
<img src="https://internetkassa.abnamro.nl/images/iDEAL_easy.gif" alt="iDEAL" />
</button>
</form>
<!-- CODE_END -->