Hi, first step is you would need to see if your BB is carrier locked, if it is, you would need to get it unlocked, that can be done here easily as there are many mobile stores that specialize in unlocking phones.
You will then need to join a BIS plan, regular plans don't work.. You can surf internet with a regular plan but that's about it, all the BB featured apps (FB, MSN, email, BBM, etc..) require a BIS plan..
I'm currently looking around for a unlimited BIS plan for personal use myself, if I find one, will let you know.. seems at the moment they are all pretty expensive compared to the other unlimited mobile internet plans 