Do some searches, you will find allot of info here. To answer your question, you have to have a provider, any can do, I would pick one based on coverage/pricing that works for you, or if you currently have a provider, that will probably work to. Since you bought the phone off ebay, is it unlocked? If not, you either have to get it unlocked or pay for an unlock code or use the provider that the BB is locked to.
Once you get a provider, you will get a email addy of
or something like that. Most people don't really use that email addy direcrtly, but just forward all existing mail to it. Therefore, no one really knows you are reading and sending email from your office or boat.