I;m not sure I understand what you are looking for. There is no network key on the S4, the key, (password) is in your router. Go to settings - connections and make certain WiFi is on then tap the left side of the WiFi connection to scan for your router. When you find it tap the connection and enter the key.
I suspect he wasn't using 'key' to refer to the WPA key/password, he was thinking there was a hard or soft button/key like on other devices that turns on the Wifi. You got him there though.
thanks guys i screwed up i meant when i try to use my phone as a portable hot spot my laptop ask for a network key.even when i use usb connection.were do i find this network that its asking for is there a video for dummies some were
it says cant connect to network is there a setting on laptop perhaps