You can find the IP address of your computer, either by opening the WiFi setup tool again. The IP address will appear at the bottom of the Window.
If you are using Occidentals, or you want to do this over a command line terminal. Open up a LXTerminal window and type the following command:
Next to the wlan0 entry you will see inet addr: 192.168.1.10 which is the IP address of the Raspberry Pi.
Remember! If your IP address starts with 192.168 or 10.0 then its an internal address - that means you can get OUT to the Internet but you cannot have someone outside your home or network reach your Pi via the IP address. This is important if you want to have a webserver running on a Pi that outside people can reach. In general, its much safer to keep your Pi on an internal network so it can't be hacked as easily!