I am trying to set up YIM on my BB and I keep getting the message that I need to visit www.blackberry.com/go/yahoo. I am doing this but there are not instructions there on how to get it to work. I have log in screen but that is as far as I can go.

Do a search under "YIM" and you will find the answer to your question. I had the same problem with my 8700c. Hope that helps. Also download it from Blackberry.com via usb then ota.