Open your Blackberry browser, go to the google saerch page and type in 'WLM for blackberry'. The first link should point to the Blackberry download site at which point select your download language, agree to the terms and it should work like a charm!
P.S.
I would post a link but I cant because I haven't posted ten times yet
I have had JiveTalk installed for a good number of months now, but at that time when I installed, for Instant Messaging, the Windows Live program did not respond in real time. I had to keep refreshing to see if messages arrived. It may not be the case anymore but, if it is, then JiveTalk is one excellent I'm program that works with all main I'm programs (all at once!)
Posted from my CrackBerry at wapforums.crackberry.com
wasn't wlm supposed to be a total package with messenger, email, etc? I was lookin for a similar app as google has for email, google talk, etc. Anthing like that for hotmail?
WLM, AIM, Google Talk, ICQ and Yahoo IM are all included with all 4.5 OSs, not sure about 4.2. You just have to edit the .alx files to get them to install.