WPA2 Key

I am a new MAC user with a MacBook Pro. I has to upgrade my wireless router from G to N. I purchased and installed the AirPort Extreme 802.11n Wi-Fi model. I did not record the information entered during the set up. In trying to connect my wife's wireless ThinkPad PC, I was asked to enter the WEP Key. How do I find that information now. Still being new to the Mac OS system, I would appreciate having this answered in a step by step process. I really need help with this. Thank you in advance.

You have already connected the mac to the network then

Then go to Applications and open up the keychain app. You will find a list of stored password, one of which should be your wireless password.

When you select an entry by double clicking you will see its details, you can then see the password by selecting the tick box and entering your admin password.

I do not know how to find applications and keychain access either. I am very new to this OS system

i am being asked for a password to access the keychain information. i do not know any of the passwords.