There are two ways you can do this (and you can find more information on any number of websites, it just takes a little looking). The first way, which is to use a normal HTML link is probably superior. I'll explain why after I give the code.
You need to create your code with your regular URL for the page you want to be referred to, and a target=_blank (or some other name, but _blank is a standard). This will create the link in a new window.
The second way is to use a Javascript, which may or may not work, I haven't tried it in the forums. Here's the code to insert:
<script language="JavaScript">
<!-- hide
function openNewWindow() {
popupWin = window.open('http://your.url.here/',
'open_window',
'menubar,toolbar,location,directories,status,scrollbars,resizable,dependent,width=640,height=480,left=0,top=0')
}
// done hiding -->
</script>
And the part that creates your link:
<a href="javascriptpenNewWindow();">Your URL description text here</a>
The second method does more of what you want, but again, I'm not sure how the forum will handle it. (hopefully it shows correctly!)
Good luck,
Z.