You need to enter the relevant security settings under the Wii's wifi configuration screen for that - and enter the SSID of your wireless point etc. Can't help without the wifi point settings... but the wii settings option is at the bottom right of the Wii channel screen I beleive...
Go to Wii Settings, search for internet connection and it will find your AP (unless it is hidden) Then enter the relevant settings and you are good to go. Wii settings, bottom left of the wii menu I believe.