On some cellular networks, the APN (Access Point Name, which identifies the Internet gateway of your cellular service provider) needs to be configured. You do not need to do any APN configuration before trying your first tethering session. You may not need this configuration (if not using a SIM card) and even if you do you may have it done already if you have any other application on your Blackberry which uses TCP/IP directly. If an APN needs to be configured on your smart phone, you will be prompted to do so by the app.
Note: Some carriers have multiple APNs and may have one having regular tether enable (with higher charge implications) and another having regular tether disabled. Bell Canada is known to be one of such carriers. You need to exercise caution in selecting which one to use. You do not need an APN with regular tether enabled when tethering with a TetherBridge app. There have been reports that some African carriers charge any usage of their APNs. This means that running any TCP/IP apps on a BlackBerry will incur additional charges regardless if it has anything to do with tethering. It is your responsibility to understand what charge policy your carrier has.
To configure your APN setting:
http://www.blackberryfaq.com/index.php/What_are_the_TCP_and_APN_settings%3F
