Trial and error seems reasonable but uh, if you're talking about doing it through your bb's options, I think you just have to be on a data plan, not positive.
Posted from my CrackBerry at wapforums.crackberry.com
You can try going to options then advanced option then host routing table. Then hit the menu key to pull up the menu and select register. That may do the trick providing you have the correct blackberry data plan.
Posted from my CrackBerry at wapforums.crackberry.com