The iPad sees the network and can pickup the signal but its not connected to the network.
Reboot your router - unplug it for about 30 seconds and then plug it back in. If the iPad will still not connect - restart it.
Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.
If that doesn't work go to Settings>General>Reset>Reset Network Settings and try again.