Right click on the icon with a red cross on it and select 'Open Network and Sharing Centre'.
You'll see several options there, try the second one 'Connect to a network' to start with.
Also you may have to install the laptop's drivers from a disk that came with it to enable the wireless connection but it's likely Win 7 will recognise the wireless connection anyway.
There will be an option somewhere to enable the wireless connection but I'm not sure where as I don't have a machine with a wireless capability with me.
But whenever I've dealt with a laptop with a wireless facility built in I've found it easy to find.
Good luck, maybe somebody else here with a built-in wireless capability can help you.