Go to http://www.avantgo.com
and create an account.
Pick the channels you want and then download the Blackberry software.
Make sure you have the new Nextel Internet Browser.
Go to Options and set the Browser to Internet Browser so it's not using the WAP browser.
Restart the Blackberry
Once that is done. Install your Blackberry Avantgo software and then sync with your Blackberry.
You will have a new Avantgo icon and you will need login once with your username and password.
Let me know if you need any help.