What exact wireless router are you trying to connect to?
To connect your cell phone via WiFi to your wireless router, you have to supply the wireless password that was confgured when the wireless router was setup. If you don't remember, log into the router and change it to something you do know. If you can't login becasue you don't know the password, use the default password as described by your manual. If that doesn't work, reset the router to factory defaults using the Reset button on the back, just press and hold it until the lights flash on the front, then reconfigure it from scatach. And save your admin and wireless passwords in a safe place, so if you forget, you can still find them.
Also make sure you are connecting to YOUR wifi network and not your neighbor's. In other words, make sure the SSID of the network you are trying to connect to matches the SSID that was configured in your router.