A BlackBerry Add On MUST ALWAYS be purchased at the same time as a goodybag for you to surf the internet with the BlackBerry Browser* as all the web traffic is routed through the BlackBerry Servers before you view it.
The £3.00 BlackBerry Add On gives you three things:
1) BlackBerry Messenger
2) BlackBerry push Email
3) Activates the BlackBerry web browser
*IT DOES NOT GIVE YOU ANY WEB ALLOWANCE OR DATA ALLOWANCE AT ALL!!!!!!!
If you use the internet regularly, I recommend the £10.00 goodybag + £3.00 BlackBerry Add On. Total price per month = £13.00. You'll get unlimited internet via official BB Web Browser, BBM and BB push Email.
Otherwise you can browse occasionally with the BlackBerry web browser (for extra data cost) if your chose the £5.00 Hokey Cokey goodybag +£3.00 BlackBerry Add On, although data charges can eat into your credit quickly with this package.
Everything you need to know about setting up your BlackBerry can be found on this post: