From the blackberry site hopefully useful. Note that the 'enter the wep/wpa code appears only to work with a T Mobile router so you are on a manual set up I think
Fist go to Manage Connections from the home screen, and then go to Set Up WiFi Network.
After that you can either; Scan For Networks, Manually Add Network, or Get Security Key.
Most users will inevitabely go with the first one, Scan For Networks, and if you select that one your device will begin to scan for available WiFi connections. Make sure that WiFi is turned on or else you will get a message telling you to do just that.
In less than one minute you should have a list of the available WiFi networks in your area. You can then choose one of the networks in your list. If you choose an unsecured network you should be connected automatically, however, if you choose a secured network then you will be asked for a security key.
If you choose the second option, Manually Add Network, then you will need to enter the network name, the type of security, as well as the security key. Your BlackBerry should then be able to connect to the network if all of your information is correct. If you don’t have all of that information, you will not be able to connect using the second option.
If you choose the third option, Get Security Key, then you will need a T-Mobile router, and on that router you would press the Key button to receive the security key and connect to a WiFi network. You can find more information about that in the T-Mobile router quick start guide, as well as your WiFi connection wizard. If you do not have a T-Mobile router, then this option is not an option for you.