first you download desktop Im from boonex, then you do the instructions it says to do, upload and do all that stuff, then you can find that link when you open your presence at the top of it, it's a little link, members click that and download desktop, but I would create a new page and insert this desktop link, or you can even do a new block using html and post it up like that. the link <tags> you use is <a href="http://www.yourwebsite.com/desktoplink">DOWNLOAD DESKTOP IM</a>
this is just the link tag to put into your new page, new block whatever, but this is not the correct path is just a demo link.
put your website and where you saved your desktop Im,