There is nothing different in setting up a Blackberry on wifi than setting up your laptop.
Either your router is set up for WEP encryption, in which case you need to select that and enter the WEP key, or it's set up for WPA-PSK in which case select that and enter the PSK. Exactly the same as you did when you set up the laptop.
The only other potential problem would be if your router has MAC Address restrictions enabled. If so you need to turn that off on the router, connect the Blackberry, add it's MAC Address to the accepted list and then re-enable MAC Address restriction.
RC